Ionically conductive compounds and related uses

ABSTRACT

Articles, compositions, and methods involving ionically conductive compounds are provided. The disclosed ionically conductive compounds may be incorporated into an electrochemical cell (e.g., a lithium-sulfur electrochemical cell, a lithium-ion electrochemical cell, an intercalated-cathode based electrochemical cell) as, for example, a protective layer for an electrode, a solid electrolyte layer, and/or any other appropriate component within the electrochemical cell. In certain embodiments, electrode structures and/or methods for making electrode structures including a layer comprising an ionically conductive compound described herein are provided.

RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.15/343,635, filed Nov. 4, 2016, which claims priority to U.S.Provisional Application No. 62/259,449, filed Nov. 24, 2015, which areincorporated herein by reference in their entirety for all purposes.

FIELD

Articles, compositions, and methods including ionically conductivecompounds are provided. In some embodiments, the ionically conductivecompounds are useful for electrochemical cells.

BACKGROUND

Lithium compound-containing electrochemical cells and batteriesincluding such cells are modern means for storing energy. They exceedcertain conventional secondary batteries with respect to capacity andlife-time and, in many times, use of toxic materials such as lead can beavoided. However, in contrast to conventional lead-based secondarybatteries, various technical problems have not yet been solved.

Secondary batteries based on cathodes including lithiated metal oxidessuch as LiCoO₂, LiMn₂O₄, and LiFePO₄ are well established. However, somebatteries of this type are limited in capacity. For that reason,numerous attempts have been made to improve the electrode materials.Particularly promising are so-called lithium sulfur batteries. In suchbatteries, lithium will be oxidized and converted to lithium sulfidessuch as Li₂S_(8-a), a being a number in the range from zero to 7. Duringrecharging, lithium and sulfur will be regenerated. Such secondary cellshave the advantage of a high capacity.

Sulfide materials of different compositions and nature are known to belithium-ion conductors (e.g., Li₂S_(x)/P₂S₅ glasses,Li₂S_(x)/P₂S₅-derived glass ceramics, Li₇P₃S₁₁, thio-LISICON, oxysulfideglasses). However, such materials may suffer from issues such as lowstability against liquid organic electrolyte solutions, insufficientstability against metallic lithium or high voltage cathode materials,extreme sensitivity to moisture and/or air, and/or an intrinsically lowionic conductivity.

Accordingly, improved lithium-ion ionically conductive compounds areneeded.

SUMMARY

Articles, compositions, and methods involving ionically conductivecompounds are provided. In some embodiments, the ionically conductivecompounds are useful for electrochemical cells.

The subject matter of the present invention involves, in some cases,interrelated products, alternative solutions to a particular problem,and/or a plurality of different uses of one or more systems and/orarticles.

In one aspect, compounds are provided. In some embodiments, the compoundhas a composition as in formula (I):Li_(2x)S_(x+w+5z)M_(y)P_(2z)  (I)wherein M is selected from the group consisting of Lanthanides, Group 3,Group 4, Group 5, Group 6, Group 7, Group 8, Group 9, Group 12, Group13, and Group 14 atoms, and combinations thereof, x is 8-16, y is 0.1-6,w is 0.1-15, and z is 0.1-3.

In certain embodiments involving the compounds described above andherein, the compound of formula (I) is crystalline. In certainembodiments involving the compounds described above and herein, thecompound of formula (I) is amorphous.

In another aspect, articles for use in an electrochemical cell isprovided. In some embodiments, the article comprises a compound offormula (I):Li_(2x)S_(x+w+5z)M_(y)P_(2z)  (I)wherein M is selected from the group consisting of Lanthanides, Group 3,Group 4, Group 5, Group 6, Group 7, Group 8, Group 9, Group 12, Group13, and Group 14 atoms, and combinations thereof, x is 8-16, y is 0.1-6,w is 0.1-15, and z is 0.1-3. In certain embodiments involving thearticles described above and herein, the article comprises a layercomprising the compound of formula (I). In certain embodiments involvingthe articles described above and herein, the article comprises thecompound of formula (I) deposited on a layer.

In yet another aspect, methods are provided. In some embodiments, themethod comprises heating a mixture of precursors comprising atoms of theelements Li, S, P, and M to a temperature ranging from 400° C. to 900°C. for a duration ranging from 3 hours to 24 hours, cooling the mixture,and forming a plurality of particles comprising a compound of formula(I):Li_(2x)S_(x+w+5z)M_(y)P_(2z)  (I),wherein M is selected from the group consisting of Lanthanides, Group 3,Group 4, Group 5, Group 6, Group 7, Group 8, Group 9, Group 12, Group13, and Group 14 atoms, and combinations thereof, x is 8-16, y is 0.1-6,w is 0.1-15, and z is 0.1-3. In certain embodiments, the mixturecomprises xLi₂S, yMS_(a), and/or zP_(b)S_(c), wherein a is 0-8, b is0-2, and c is 0-8, such that b+c is 1 or greater.

In some embodiments, the method comprises depositing a plurality ofparticles comprising a compound of formula (I) on a layer:Li_(2x)S_(x+w+5z)MyP_(2z)  (I)wherein M is selected from the group consisting of Lanthanides, Group 3,Group 4, Group 5, Group 6, Group 7, Group 8, Group 9, Group 12, Group13, and Group 14 atoms, and combinations thereof, x is 8-16, y is 0.1-6,w is 0.1-15, and z is 0.1-3.

In certain embodiments involving the methods described above and herein,prior to heating, the mixture is mixed by ball milling. In certainembodiments involving the methods described above and herein, heatingthe mixture occurs at a pressure of between 0.1 MPa and 0.3 MPa. Incertain embodiments involving the methods described above and herein,depositing the plurality of particles comprising the compound of formula(I) on the layer comprises aerosol deposition or vacuum deposition. Incertain embodiments involving the methods described above and herein,the layer on which the particles are deposited is an electrode, alithium metal layer, a protective layer, or a separator.

In certain embodiments involving the compounds, articles, and/or methodsdescribed above and herein, x is 10 or greater.

In certain embodiments involving the compounds, articles, and/or methodsdescribed above and herein, y is 1.

In certain embodiments involving the compounds, articles, and/or methodsdescribed above and herein, w is equal to y, 1.5y, or 2y.

In certain embodiments involving the compounds, articles, and/or methodsdescribed above and herein, z is 1.

In certain embodiments involving the compounds, articles, and/or methodsdescribed above and herein, M is selected from the group consisting ofsilicon, tin, germanium, zinc, iron, zirconium, aluminum, andcombinations thereof.

In certain embodiments involving the compounds, articles, and/or methodsdescribed above and herein, the compound of formula (I) has a cubicstructure.

In certain embodiments involving the articles and/or methods describedabove and herein, the article or method comprises a plurality ofparticles that comprise the compound of formula (I). In certainembodiments involving the articles and/or methods described above andherein, the article or method comprises a layer comprising a pluralityof particles that comprise the compound of formula (I). In certainembodiments involving the articles and/or methods described above andherein, the plurality of particles have an average largestcross-sectional dimension of greater than or equal to 10 nm and lessthan or equal to 100 microns. In certain embodiments involving thearticles and/or methods described above and herein, the plurality ofparticles have an average ion conductivity of greater than or equal to10⁻⁴ S/cm.

In certain embodiments involving the articles and/or methods describedabove and herein, the layer comprising the compound of formula (I) is indirect contact with the electrode.

In certain embodiments involving the articles and/or methods describedabove and herein, the layer comprising the compound of formula (I) is aseparator. In certain embodiments involving the articles and/or methodsdescribed above and herein, the layer comprising the compound of formula(I) has an average thickness of greater than or equal to 1 microns andless than or equal to 50 microns.

In certain embodiments involving the articles and/or methods describedabove and herein, the layer comprising the compound of formula (I) is aprotective layer. In certain embodiments involving the articles and/ormethods described above and herein, the layer comprising the compound offormula (I) has an average thickness of greater than or equal to 1nanometer and less than or equal to 10 microns.

In certain embodiments involving the articles and/or methods describedabove and herein, the layer comprising the compound of formula (I) is asolid electrolyte layer. In certain embodiments involving the articlesand/or methods described above and herein, the layer comprising thecompound of formula (I) has an average thickness of greater than orequal to 50 nm and less than or equal to 25 microns.

In certain embodiments involving the articles and/or methods describedabove and herein, the layer comprising the compound of formula (I) is alithium-intercalation electrode. In certain embodiments involving thearticles and/or methods described above and herein, the layer comprisingthe compound of formula (I) has an average ion conductivity of greaterthan or equal to 10⁻⁴ S/cm.

In certain embodiments involving the articles and/or methods describedabove and herein, at least a portion of the layer comprising thecompound of formula (I) is crystalline. In certain embodiments involvingthe articles and/or methods described above and herein, the layercomprising the compound of formula (I) is amorphous.

In yet another aspect, electrochemical cells are provided. In someembodiments, the electrochemical cell comprises an article as describedabove and herein. In certain embodiments involving the electrochemicalcells described above and herein, the electrochemical cell comprises aliquid electrolyte, an anode comprising lithium or silicon, and/or acathode comprising sulfur or a lithium-intercalation species.

Other advantages and novel features of the present invention will becomeapparent from the following detailed description of various non-limitingembodiments of the invention when considered in conjunction with theaccompanying figures. In cases where the present specification and adocument incorporated by reference include conflicting and/orinconsistent disclosure, the present specification shall control. If twoor more documents incorporated by reference include conflicting and/orinconsistent disclosure with respect to each other, then the documenthaving the later effective date shall control.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting embodiments of the present invention will be described byway of example with reference to the accompanying figures, which areschematic and are not intended to be drawn to scale. In the figures,each identical or nearly identical component illustrated is typicallyrepresented by a single numeral. For purposes of clarity, not everycomponent is labeled in every figure, nor is every component of eachembodiment of the invention shown where illustration is not necessary toallow those of ordinary skill in the art to understand the invention. Inthe figures:

FIGS. 1A-1E are a schematics of articles incorporating ionicallyconductive compounds, according to some embodiments;

FIG. 2 is a plot of conductivity (in S/cm) as a function of x for acompound having a formula as in Li_(2x)S_(x+7)SiP₂, according to someembodiments;

FIG. 3 is an XRD spectral plot of Li₁₀S₁₂SiP₂ and Li₂₀S₁₇SiP₂, accordingto one set of embodiments;

FIG. 4 is an XRD spectral plot of Li₁₀S₁₂SiP₂ and Li₂₄S₁₉SiP₂, accordingto one set of embodiments; and

FIG. 5 is an XRD spectral plot of Li₂₀S₁₇SiP₂ before and afterelectrolyte exposure, according to one set of embodiments.

FIG. 6 is an XRD spectral plot of Li₂₂SiP₂S₁₈ before and afterelectrolyte exposure, according to one set of embodiments.

FIG. 7 is an XRD spectral plot of Li₁₈P₃S₁₅Br₃ before and afterelectrolyte exposure, according to one set of embodiments.

DETAILED DESCRIPTION

Articles, compositions, and methods involving ionically conductivecompounds are provided. In some embodiments, the ionically conductivecompounds are useful for electrochemical cells. The disclosed ionicallyconductive compounds may be incorporated into an electrochemical cell(e.g., a lithium-sulfur electrochemical cell, a lithium-ionelectrochemical cell, an intercalated-cathode based electrochemicalcell) as, for example, a protective layer for an electrode, a solidelectrolyte layer, and/or any other appropriate component within theelectrochemical cell. In certain embodiments, electrode structuresand/or methods for making electrode structures including a layercomprising an ionically conductive compound described herein areprovided.

The incorporation of ionically conductive compounds as described hereininto electrochemical cells may, for example, increase the stability ofan electrode (e.g., a lithium electrode) in the electrochemical cell,increase ionic conductivity, and/or may facilitate fabrication (e.g.,formation of thin layers), as compared to certain existing ionicallyconductive compounds used in electrochemical cells. In some embodiments,the incorporation of ionically conductive compounds as described hereininto electrochemical cells may prevent or reduce the occurrence ofchemical reactions between a component of an electrolyte (e.g.,polysulfides) and an electroactive material of an anode (e.g., an anodecomprising lithium, such as metallic lithium).

Layers comprising the ionically conductive compound, as described inmore detail herein, may, in some cases, selectively conduct lithiumcations but not anions, and may function as a barrier (e.g., protectivestructure) for electrolytes (e.g., liquid electrolytes). For example,the use of the ionically conductive compounds in a protective layer(e.g., in an electrochemical cell including a liquid electrolyte) mayoffer several advantages over certain existing protective layers,including reduction in the consumption of lithium (e.g., lithium metal)during charge/discharge of the electrochemical cell. The protectivelayer may be used to substantially inhibit direct contact of anelectrode (e.g., the anode, the cathode) with an electrolyte and/or aparticular species present in the electrolyte. In some embodiments, theuse of ionically conductive compounds described herein in solidelectrolyte layers (e.g., in solid state electrochemical cells) mayoffer several advantages over certain existing solid electrolytesincluding increased ion conductivity and/or increased chemicalstability.

The disclosed ionically conductive compounds may be incorporated intoelectrochemical cells including primary batteries or secondarybatteries, which can be charged and discharged numerous times. Incertain embodiments, the articles, compositions, and methods describedherein can be used in association with batteries including a liquidelectrolyte. However, in other embodiments, the articles, compositions,and methods described herein can be used in association with solid statebatteries.

In some embodiments, the materials, systems, and methods describedherein can be used in association with lithium batteries (e.g.,lithium-sulfur batteries). It should be appreciated, however, that whilemuch of the description herein relates to lithium-sulfur batteries, theionically conductive compounds and layers comprising ionicallyconductive compounds described herein may be applied to otherlithium-based batteries, including other alkali metal-based batteries.

The electrochemical cells described herein may be employed in variousapplications, for example, making or operating cars, computers, personaldigital assistants, mobile telephones, watches, camcorders, digitalcameras, thermometers, calculators, laptop BIOS, communication equipmentor remote car locks.

In some embodiments, the ionically conductive compound has a compositionas in formula (I):Li_(2x)S_(x+w+5z)M_(y)P_(2z)  (I),where x is 8-16, y is 0.1-6, w is 0.1-15, z is 0.1-3, and M is selectedfrom the group consisting of Lanthanides, Group 3, Group 4, Group 5,Group 6, Group 7, Group 8, Group 9, Group 12, Group 13, and Group 14atoms, and combinations thereof.

In some embodiments, the ionically conductive compound has a compositionas in formula (I) and x is 8-16, 8-12, 10-12, 10-14, or 12-16. In someembodiments x is 8 or greater, 8.5 or greater, 9 or greater, 9.5 orgreater, 10 or greater, 10.5 or greater, 11 or greater, 11.5 or greater,12 or greater, 12.5 or greater, 13 or greater, 13.5 or greater, 14 orgreater, 14.5 or greater, 15 or greater, or 15.5 or greater. In certainembodiments, x is less than or equal to 16, less than or equal to 15.5,less than or equal to 15, less than or equal to 14.5, less than or equalto 14, less than or equal to 13.5, less than or equal to 13, less thanor equal to 12.5, less than or equal to 12, less than or equal to 11.5,less than or equal to 11, less than or equal to 10.5, less than or equalto 10, less than or equal to 9.5, or less than or equal to 9.Combinations of the above referenced ranges are also possible (e.g.,greater than or equal to 8 and less than or equal to 16, greater than orequal to 10 and less than or equal to 12). Other ranges are alsopossible. In some embodiments, x is 10. In certain embodiments, x is 12.

In certain embodiments, the ionically conductive compound has acomposition as in formula (I) and y is 0.1-6, 0.1-1, 0.1-3, 0.1-4.5,0.1-6, 0.8-2, 1-4, 2-4.5, 3-6 or 1-6. For example, in some embodiments,y is 1. In some embodiments, y is greater than or equal to 0.1, greaterthan or equal to 0.2, greater than or equal to 0.4, greater than orequal to 0.5, greater than or equal to 0.6, greater than or equal to0.8, greater than or equal to 1, greater than or equal to 1.2, greaterthan or equal to 1.4, greater than or equal to 1.5, greater than orequal to 1.6, greater than or equal to 1.8, greater than or equal to2.0, greater than or equal to 2.2, greater than or equal to 2.4, greaterthan or equal to 2.5, greater than or equal to 2.6, greater than orequal to 2.8, greater than or equal to 3.0, greater than or equal to3.5, greater than or equal to 4.0, greater than or equal to 4.5, greaterthan or equal to 5.0, or greater than or equal to 5.5. In certainembodiments, y is less than or equal to 6, less than or equal to 5.5,less than or equal to 5.0, less than or equal to 4.5, less than or equalto 4.0, less than or equal to 3.5, less than or equal to 3.0, less thanor equal to 2.8, less than or equal to 2.6, less than or equal to 2.5,less than or equal to 2.4, less than or equal to 2.2, less than or equalto 2.0, less than or equal to 1.8, less than or equal to 1.6, less thanor equal to 1.5, less than or equal to 1.4, less than or equal to 1.2,less than or equal to 1.0, less than or equal to 0.8, less than or equalto 0.6, less than or equal to 0.5, less than or equal to 0.4, or lessthan or equal to 0.2. Combinations of the above-referenced ranges arealso possible (e.g., greater than or equal to 0.1 and less than or equalto 6.0, greater than or equal to 1 and less than or equal to 6, greaterthan or equal to 1 and less than or equal to 3, greater than or equal to0.1 and less than or equal to 4.5, greater than or equal to 1.0 and lessthan or equal to 2.0). Other ranges are also possible. In embodiments inwhich a compound of formula (I) includes more than one M, the total ymay have a value in one or more of the above-referenced ranges and insome embodiments may be in the range of 0.1-6.

In some embodiments, the ionically conductive compound has a compositionas in formula (I) and z is 0.1-3, 0.1-1, 0.8-2, or 1-3. For example, insome embodiments, z is 1. In some embodiments, z is greater than orequal to 0.1, greater than or equal to 0.2, greater than or equal to0.4, greater than or equal to 0.5, greater than or equal to 0.6, greaterthan or equal to 0.8, greater than or equal to 1, greater than or equalto 1.2, greater than or equal to 1.4, greater than or equal to 1.5,greater than or equal to 1.6, greater than or equal to 1.8, greater thanor equal to 2.0, greater than or equal to 2.2, greater than or equal to2.4, greater than or equal to 2.5, greater than or equal to 2.6, orgreater than or equal to 2.8. In certain embodiments, z is less than orequal to 3.0, less than or equal to 2.8, less than or equal to 2.6, lessthan or equal to 2.5, less than or equal to 2.4, less than or equal to2.2, less than or equal to 2.0, less than or equal to 1.8, less than orequal to 1.6, less than or equal to 1.5, less than or equal to 1.4, lessthan or equal to 1.2, less than or equal to 1.0, less than or equal to0.8, less than or equal to 0.6, less than or equal to 0.5, less than orequal to 0.4, or less than or equal to 0.2. Combinations of theabove-referenced ranges are also possible (e.g., greater than or equalto 0.1 and less than or equal to 3.0, greater than or equal to 1.0 andless than or equal to 2.0). Other ranges are also possible.

In certain embodiments, the ratio of y to z is greater than or equal to0.03, greater than or equal to 0.1, greater than or equal to 0.25,greater than or equal to 0.5, greater than or equal to 0.75, greaterthan or equal to 1, greater than or equal to 2, greater than or equal to4, greater than or equal to 8, greater than or equal to 10, greater thanor equal to 15, greater than or equal to 20, greater than or equal to25, greater than or equal to 30, greater than or equal to 40, greaterthan or equal to 45, or greater than or equal to 50. In someembodiments, the ratio of y to z is less than or equal to 60, less thanor equal to 50, less than or equal to 45, less than or equal to 40, lessthan or equal to 30, less than or equal to 25, less than or equal to 20,less than or equal to 15, less than or equal to 10, less than or equalto 8, less than or equal to 4, less than or equal to 3, less than orequal to 2, less than or equal to 1, less than or equal to 0.75, lessthan or equal to 0.5, less than or equal to 0.25, or less than or equalto 0.1. Combinations of the above-referenced ranges are also possible(e.g., a ratio of y to z of greater than or equal to 0.1 and less thanor equal to 60, a ratio of y to z of greater than or equal to 0.1 andless than or equal to 10, greater than or equal to 0.25 and less than orequal to 4, or greater than or equal to 0.75 and less than or equal to2). In some embodiments, the ratio of y to z is 1.

In some embodiments, the ionically conductive compound has a compositionas in formula (I) and w is 0.1-15, 0.1-1, 0.8-2, 1-3, 1.5-3.5, 2-4,2.5-5, 3-6, 4-8, 6-10, 8-12, or 10-15. For example, in some embodiments,w is 1. In some cases, w may be 1.5. In certain embodiments, w is 2. Insome embodiments, w is greater than or equal to 0.1, greater than orequal to 0.2, greater than or equal to 0.4, greater than or equal to0.5, greater than or equal to 0.6, greater than or equal to 0.8, greaterthan or equal to 1, greater than or equal to 1.5, greater than or equalto 2, greater than or equal to 2.5, greater than or equal to 3, greaterthan or equal to 4, greater than or equal to 6, greater than or equal to8, greater than or equal to 10, greater than or equal to 12, or greaterthan or equal to 14. In certain embodiments, w is less than or equal to15, less than or equal to 14, less than or equal to 12, less than orequal to 10, less than or equal to 8, less than or equal to 6, less thanor equal to 4, less than or equal to 3, less than or equal to 2.5, lessthan or equal to 2, less than or equal to 1.5, less than or equal to 1,less than or equal to 0.8, less than or equal to 0.6, less than or equalto 0.5, less than or equal to 0.4, or less than or equal to 0.2.Combinations of the above-referenced ranges are also possible (e.g.,greater than or equal to 0.1 and less than or equal to 15, greater thanor equal to 1.0 and less than or equal to 3.0). Other ranges are alsopossible.

In an exemplary embodiment, the ionically conductive compound has acomposition as in Li₁₆S₁₅MP₂. In another exemplary embodiment, theionically conductive compound has a composition as in Li₂₀S₁₇MP₂. In yetanother exemplary embodiment, the ionically conductive compound has acomposition as in Li₂₁S₁₇Si₂P. In yet another exemplary embodiment, theionically conductive compound has a composition as in Li₂₄S₁₉MP₂. Forexample an ionically conductive compound according to the presentinvention has a composition according to a formula selected from thegroup consisting of Li₁₆S₁₅MP₂, Li₂₀S₁₇MP₂ and Li₂₄S₁₉MP₂.

In some embodiments, w is equal to y. In certain embodiments, w is equalto 1.5y. In other embodiments, w is equal to 2y. In yet otherembodiments, w is equal to 2.5y. In yet further embodiments, w is equalto 3y. Without wishing to be bound by theory, those skilled in the artwould understand that the value of w may, in some cases, depend upon thevalency of M. For example, in some embodiments, M is a tetravalent atom,w is 2y, and y is 0.1-6. In certain embodiments, M is a trivalent atom,w is 1.5y, and y is 0.1-6. In some embodiments, M is a bivalent atom, wis equal to y, and y is 0.1-6. Other valences and values for w are alsopossible.

In some embodiments, the ionically conductive compound has a compositionas in formula (I) and M is tetravalent, x is 8-16, y is 0.1-6, w is 2y,and z is 0.1-3. In some such embodiments, the ionically conductivecompound has a composition as in formula (II):Li_(2x)S_(x+2y+5z)M_(y)P_(2z)  (II)where x is 8-16, y is 0.1-6, z is 0.1-3, and M is tetravalent andselected from the group consisting of Lanthanides, Group 4, Group 8,Group 12, and Group 14 atoms, and combinations thereof. In an exemplaryembodiment, M is Si, x is 10.5, y is 1, and z is 1 such that thecompound of formula (II) is Li₂₁S_(17.5)SiP₂.

In some embodiments, the ionically conductive compound has a compositionas in formula (I) and M is trivalent, x is 8-16, y is 1, w is 1.5y, andz is 1. In some such embodiments, the ionically conductive compound hasa composition as in formula (III):Li_(2x)S_(x+1.5y+5z)M_(y)P_(2z)  (III),where x is 8-16, y is 0.1-6, z is 0.1-3, and M is trivalent and selectedfrom the group consisting of Lanthanides, Group 3, Group 4, Group 5,Group 6, Group 7, Group 8, Group 9, Group 12, Group 13, and Group 14atoms, and combinations thereof. In an exemplary embodiment, M is Ga, xis 10.5, y is 1, and z is 1 such that the compound of formula (III) isLi₂₁S₁₇GaP₂.

In some embodiments, M is a Group 4 (i.e. IUPAC Group 4) atom such aszirconium. In certain embodiments, M is a Group 8 (i.e. IUPAC Group 8)atom such as iron. In some embodiments, M is a Group 12 (i.e. IUPACGroup 12) atom such as zinc. In certain embodiments, M is a Group 13(i.e. IUPAC Group 13) atom such as aluminum. In some embodiments, M is aGroup 14 (i.e. IUPAC Group 14) atom such as silicon, germanium, or tin.In some cases, M may be selected from the groups consisting ofLanthanides, Group 3, Group 4, Group 5, Group 6, Group 7, Group 8, Group9, Group 12, Group 13, and/or Group 14 atoms. For example, in someembodiments, M may be selected from silicon, tin, germanium, zinc, iron,zirconium, aluminum, and combinations thereof. In certain embodiments, Mis selected from silicon, germanium, aluminum, iron and zinc. In someembodiments, M is a transition metal atom.

In some cases, M may be a combination of two or more atoms selected fromthe groups consisting of Lanthanides, Group 3, Group 4, Group 5, Group6, Group 7, Group 8, Group 9, Group 12, Group 13, and Group 14 atoms.That is, in certain embodiments in which M includes more than one atom,each atom (i.e. each atom M) may be independently selected from thegroup consisting of Lanthanides, Group 3, Group 4, Group 5, Group 6,Group 7, Group 8, Group 9, Group 12, Group 13, and Group 14 atoms. Insome embodiments, M is a single atom. In certain embodiments, M is acombination of two atoms. In other embodiments, M is a combination ofthree atoms. In some embodiments, M is a combination of four atoms. Insome embodiments, M may be a combination of one or more monovalentatoms, one or more bivalent atoms, one or more trivalent atoms, and/orone or more tetravalent atoms selected from the groups consisting ofLanthanides, Group 3, Group 4, Group 5, Group 6, Group 7, Group 8, Group9, Group 12, Group 13, and Group 14 atoms.

In such embodiments, the stoichiometric ratio of each atom in M may besuch that the total amount of atoms present in M is y and is 0.1-6, orany other suitable range described herein for y. For example, in someembodiments, M is a combination of two atoms such that the total amountof the two atoms present in M is y and is 0.1-6. In certain embodiments,each atom is present in M in substantially the same amount and the totalamount of atoms present in M is y and within the range 0.1-6, or anyother suitable range described herein for y. In other embodiments, eachatom may be present in M in different amounts and the total amount ofatoms present in M is y and within the range 0.1-6, or any othersuitable range described herein for y. In an exemplary embodiment, theionically conductive compound has a composition as in formula (I) andeach atom in M is either silicon or germanium and y is 0.1-6. Forexample, in such an embodiment, each atom in M may be either silicon orgermanium, each present in substantially the same amount, and y is 1since M_(y) is Si_(0.5)Ge_(0.5). In another exemplary embodiment, theionically conductive compound has a composition as in formula (I) andeach atom in M may be either silicon or germanium, each atom present indifferent amounts such that M_(y) is Si_(y-p)Ge_(p), where p is between0 and y (e.g., y is 1 and p is 0.25 or 0.75). Other ranges andcombinations are also possible. Those skilled in the art wouldunderstand that the value and ranges of y, in some embodiments, maydepend on the valences of M as a combination of two or more atoms, andwould be capable of selecting and/or determining y based upon theteachings of this specification. As noted above, in embodiments in whicha compound of formula (I) includes more than one atom in M, the total ymay be in the range of 0.1-6.

In an exemplary embodiment, M is silicon. For example, in someembodiments, the ionically conductive compound isLi_(2x)S_(x+w+5z)Si_(y)P_(2z), where x is greater than or equal to 8 andless than or equal to 16, y is greater than or equal to 0.1 and lessthan or equal to 3, w is equal to 2y, and z is greater than or equal to0.1 and less than or equal to 3. Each x, y and z may independently bechosen from the values and ranges of x, y and z described above,respectively. For example, in one particular embodiment, x is 10, y is1, and z is 1, and the ionically conductive compound is Li₂₀S₁₇SiP₂. Insome embodiments, x is 10.5, y is 1, and z is 1, and the ionicallyconductive compound is Li₂₁S_(17.5)SiP₂. In certain embodiments, x is11, y is 1, and z is 1, and the ionically conductive compound isLi₂₂S₁₈SiP₂. In certain embodiments, x is 12, y is 1, and z is 1, andthe ionically conductive compound is Li₂₄S₁₉SiP₂. In some cases, x is14, y is 1, and z is 1, and the ionically conductive compound isLi₂₈S₂₁SiP₂. In yet another exemplary embodiment, M is a combination oftwo atoms, wherein the first atom is Si and the second atom is selectedfrom the groups consisting of Lanthanides, Group 3, Group 4, Group 5,Group 6, Group 7, Group 8, Group 9, Group 12, Group 13, and Group 14atoms. For example, in some embodiments, the ionically conductivecompound is Li_(2x)S_(x+w+5z)Si_(a)Q_(b)P_(2z) where Q is selected fromthe groups consisting of Lanthanides, Group 3, Group 4, Group 5, Group6, Group 7, Group 8, Group 9, Group 12, Group 13, and Group 14 atoms,a+b=y, and each w, x, y and z may independently be chosen from thevalues and ranges of w, x, y and z described above, respectively. Insome embodiments, the ionically conductive compound isLi₂₁La_(0.5)Si_(1.5)PS_(16.75). In certain embodiments, the ionicallyconductive compound is Li₂₁LaSiPS_(16.75). In certain embodiments, theionically conductive compound is Li₂₁AlSiPS_(16.5). In certainembodiments, the ionically conductive compound isLi₂₁Al_(0.5)Si_(1.5)PS_(16.75). In certain embodiments, the ionicallyconductive compound is Li₂₁AlSi₂S₁₆. In certain embodiments, theionically conductive compound is Li₂₁BP₂S₁₇.

It should be appreciated that while much of the above description hereinrelates to ionically conductive compounds where y is 1, z is 1, w is 2y,and comprises silicon, other combinations of values for w, x, y, and zand elements for M are also possible. For example, in some cases, M isGe and the ionically conductive compound may beLi_(2x)S_(x+w+5z)Ge_(y)P_(2z), where x is greater than or equal to 8 andless than or equal to 16, y is greater than or equal to 0.1 and lessthan or equal to 3, w is equal to 2y, and z is greater than or equal to0.1 and less than or equal to 3. Each w, x, y and z may independently bechosen from the values and ranges of w, x, y and z described above,respectively. For example, in one particular embodiment, w is 2, x is10, y is 1, and z is 1, and the ionically conductive compound isLi₂₀S₁₇GeP₂. In certain embodiments, w is 2, x is 12, y is 1, and z is1, and the ionically conductive compound is Li₂₄S₁₉GeP₂. In some cases,w is 2, x is 14, y is 1, and z is 1, and the ionically conductivecompound is Li₂₈S₂₁GeP₂. Other stoichiometric ratios, as describedabove, are also possible.

In certain embodiments, M is Sn and the ionically conductive compoundmay be Li_(2x)S_(x+w+5z)Sn_(y)P_(2z), where x is greater than or equalto 8 and less than or equal to 16, y is greater than or equal to 0.1 andless than or equal to 3, w is equal to 2y, and z is greater than orequal to 0.1 and less than or equal to 3. Each w, x, y and z mayindependently be chosen from the values and ranges of w, x, y and zdescribed above, respectively. For example, in one particularembodiment, w is 2, x is 10, y is 1, and z is 1, and the ionicallyconductive compound is Li₂₀S₁₇SnP₂. In certain embodiments, w is 2, x is12, y is 1, and z is 1, and the ionically conductive compound isLi₂₄S₁₉SnP₂. In some cases, w is 2, x is 14, y is 1, and z is 1, and theionically conductive compound is Li₂₈S₂₁SnP₂. Other stoichiometricratios, as described above, are also possible.

In an exemplary embodiment, the ionically conductive compound has acomposition as in formula (I):Li_(2x)S_(x+w+5z)M_(y)P_(2z)  (I)wherein x is 5-14, y is 1-2, z is 0.5-1, (x+w+5z) is 12-21, and M isselected from the group consisting of Si, Ge, La, Al, B, Ga, andcombinations thereof (e.g., such that M_(y) is La_(0.5)Si_(1.5), LaSi,AlSi, Al_(0.5)Si_(1.5), or AlSi₂). Non-limiting examples of compoundshaving a composition as in formula (I) include Li₁₀S₁₂SiP₂, Li₁₂S₁₃SiP₂,Li₁₆S₁₅SiP₂, Li₂₀S₁₇SiP₂, Li₂₁S₁₇Si₂P, Li₂₁S_(17.5)SiP₂, Li₂₂S₁₈SiP₂,Li₂₄S₁₉SiP₂, Li₂₈S₂₁SiP₂, Li₂₄S₁₉GeP₂, Li₂₁SiP₂S_(17.5),Li₂₁La_(0.5)Si_(1.5)PS_(16.75), Li₂₁LaSiPS_(16.5), Li₂₁La₂PS₁₆,Li₂₁AlP₂S₁₇, Li₁₇AlP₂S₁₅, Li₁₇Al₂PS₁₄, Li₁₁AlP₂S₁₂, Li₁₁AlP₂S₁₂,Li₂₁AlSiPS_(16.5), Li₂₁Al_(0.5)Si_(1.5)PS_(16.75), Li₂₁AlSi₂S₁₆,Li₂₁BP₂S₁₇, and Li₂₁GaP₂S₁₇. Other compounds are also possible.

In some embodiments, the ionically conductive compound (e.g., theionically conductive compound of formula (I)) is in the form of aparticle. A plurality of particles comprising the ionically conductivecompound may be substantially ionically conductive (e.g., substantiallyconductive to lithium ions). For example, in certain embodiments, aplurality of particles comprising the ionically conductive compound maybe conductive to ions of an electroactive material (e.g. lithium). Insome cases, the plurality of particles may have an average ionconductivity (e.g., lithium ion conductivity) of greater than or equalto 10⁻⁴ S/cm. In certain embodiments, the average ion conductivity ofthe plurality of particles is greater than or equal to greater than orequal to 10⁻⁴ S/cm, greater than or equal to 10⁻³ S/cm, greater than orequal to 10⁻² S/cm, or greater than or equal to 10⁻¹ S/cm. In someembodiments, the average ion conductivity of the plurality of particlesis less than or equal to 1 S/cm, less than or equal to 10⁻¹ S/cm, lessthan or equal to 10⁻² S/cm, or less than or equal to 10⁻³ S/cm.Combinations of the above-reference ranges are also possible (e.g., anion conductivity greater than or equal to 10⁻⁴ S/cm and less than orequal to 10⁻¹ S/cm, greater than or equal to 10⁻⁴ S/cm and less than orequal to 10⁻² S/cm). Other ion conductivities are also possible.

In some embodiments, the average ion conductivity of the plurality ofparticles can be determined before the particles are incorporated into alayer of an electrochemical cell (e.g., a protective layer, a solidelectrolyte layer, an intercalated electrode layer). The average ionicconductivity can be measured by pressing the particles between twocopper cylinders at a pressure of up to 4 tons/cm². In certainembodiments, the average ion conductivity (i.e., the inverse of theaverage resistivity) can be measured at 500 kg/cm² increments using aconductivity bridge (i.e., an impedance measuring circuit) operating at1 kHz. In some such embodiments, the pressure is increased until changesin average ion conductivity are no longer observed in the sample.Conductivity may be measured at room temperature (e.g., 25 degreesCelsius).

In some embodiments, the average largest cross-sectional dimension of aplurality of particles (e.g., within a layer of an electrochemical cell,or prior to being incorporated into a layer) comprising the ionicallyconductive compound may be, for example, less than or equal to 100microns, less than or equal to 50 microns, less than or equal to 25microns, less than or equal to 10 microns, less than or equal to 5microns, less or equal to 2 microns, less than or equal to 1 micron,less than or equal to 500 nm, less than or equal to 100 nm, or less thanor equal to 50 nm. In some embodiments, the average largestcross-sectional dimension of the plurality of particles may be greaterthan or equal to 10 nm, greater than or equal to 100 nm, greater than orequal to 500 nm, greater than or equal to 1 micron, greater than orequal to 2 microns, greater than or equal to 5 microns, greater than orequal to 10 microns, greater than or equal to 25 microns, or greaterthan or equal to 50 microns. Combinations of the above-referenced rangesare also possible (e.g., a largest cross-sectional dimension of lessthan 100 microns and greater than 10 microns, less than 25 microns andgreater than 1 micron, less than 2 microns and greater than 100 nm, lessthan 500 nm and greater than 10 nm).

The average largest cross-sectional dimension of the plurality ofparticles may be determined, for example, by imaging the particles witha scanning electron microscope (SEM). An image may be acquired at amagnification between 10× to 100,000×, depending on the overalldimensions of the plurality of particles. Those skilled in the art wouldbe capable of selecting an appropriate magnification for imaging thesample. The average largest cross-sectional dimension of the pluralityof particles can be determined by taking the longest cross-sectionaldimension of each particle and averaging the longest cross-sectionaldimensions (e.g., averaging the longest cross-sectional dimensions for10 particles).

In some embodiments, particles comprising an ionically conductivecompound described herein may be formed by heating a mixture ofprecursors, as described in more detail herein. In certain embodiments,the precursors comprise a mixture of the elements Li, S, P, and M, whereM is as described above and is selected from the group consisting ofLanthanides, Group 3, Group 4, Group 5, Group 6, Group 7, Group 8, Group9, Group 12, Group 13, and Group 14 atoms of the periodic system ofelements, and combinations thereof. In some embodiments, the elementsLi, S, P, and M are present either in elemental form or in chemicallybound form. For example, Li may be provided in chemically bound form,such as in the form of a chemical compound comprising Li and atoms ofone or more of the elements S, P, and M as described above (e.g., Li₂S.M, P and S may be provided in elemental form). In some embodiments, theprecursors comprise a mixture of the elements Li, S, P, and Si. Incertain embodiments, the precursors comprise a mixture of the elementsLi, S, P, and Ge. In some cases, the precursors may comprise a mixtureof the elements Li, S, P, and Sn.

In some embodiments, at least a portion of the precursors are selectedfrom the group consisting of xLi₂S, yMS_(a), and/or zP_(b)S_(c), where xis 8-16, y is 0.1-6, z is 0.1-3, a is 0-8, b is 0-2, and c is 0-8 suchthat b+c is 1 or greater. For example, in some embodiments, x is 10-14,y is 1, a is 0-8, b is 1-2, and c is 2-5. In some embodiments, at leasta portion of the precursors are selected from the group consisting ofLi₂S, MS_(a), and P_(b)S_(c), where a is 0-8, b is 0-2, and c is 0-8such that b+c is 1 or greater. For example, in some such embodiments, ais 0-8, b is 1-2, and c is 2-5. Non-limiting examples of suitableprecursors include Li₂S, SiS₂, GeS₂, SnS₂, Si, Ge, Sn, S₂, S₄, S₈, P₂S₅,P, and combinations thereof.

In some embodiments, a is greater than or equal to 0, greater than orequal to 1, greater than or equal to 2, greater than or equal to 3,greater than or equal to 4, greater than or equal to 5, greater than orequal to 6, or greater than or equal to 7. In certain embodiments, a isless than or equal to 8, less than or equal to 7, less than or equal to6, less than or equal to 5, less than or equal to 4, less than or equalto 3, or less than or equal to 2. Combinations of the above-referencedranges are also possible (e.g., greater than or equal to 0 and less thanor equal to 8, greater than or equal to 1 and less than or equal to 4,greater than or equal to 2 and less than or equal to 6, greater than orequal to 4 and less than or equal to 8). In some cases, a may be 0,(i.e. the precursor is elemental M).

In certain embodiments, b is greater than or equal to 0, or greater thanor equal to 1. In some cases, b may be less than or equal to 2, or lessthan or equal to 1. Combinations of the above-referenced ranges are alsopossible (e.g., greater than or equal to 0 and less than or equal to 2).In some embodiments, b is 0 (i.e., the precursor is elemental sulfur).In certain embodiments, b is 1. In some cases, b may be 2.

In some embodiments, c is greater than or equal to 0, greater than orequal to 1, greater than or equal to 2, greater than or equal to 3,greater than or equal to 4, greater than or equal to 5, greater than orequal to 6, or greater than or equal to 7. In certain embodiments, c isless than or equal to 8, less than or equal to 7, less than or equal to6, less than or equal to 5, less than or equal to 4, less than or equalto 3, or less than or equal to 2. Combinations of the above-referencedranges are also possible (e.g., greater than or equal to 0 and less thanor equal to 8, greater than or equal to 1 and less than or equal to 4,greater than or equal to 2 and less than or equal to 6, greater than orequal to 4 and less than or equal to 8). In certain embodiments, c is 0(i.e., the precursor is elemental phosphor). In some embodiments, c is1.

In some embodiments, b and c are selected such that b+c is 1 or greater(e.g., 2 or greater, 3 or greater, 4 or greater, 5 or greater, 6 orgreater, 7 or greater, 8 or greater, or 9 or greater). In some cases b+cis less than or equal to 10, less than or equal to 9, less than or equalto 8, less than or equal to 7, less than or equal to 6, less than orequal to 5, less than or equal to 4, less than or equal to 3, or lessthan or equal to 2. Combinations of the above-referenced ranges are alsopossible.

In an exemplary embodiment, at least some of the precursors are selectedfrom the group consisting of xLi₂S, yMS_(a), and/or zP_(b)S_(c), and xis 10, y is 1, z is 1, a is 2, b is 2 and c is 5.

In certain embodiments, a mixture of precursors described herein has astoichiometric ratio of the elements Li, S, P, and M as in formula (I),as described above (i.e., Li_(2x)S_(x+w+5z)M_(y)P_(2z)). In someembodiments, Li, S, P, and M have a stoichiometric ratio such that theplurality of particles formed from the mixture comprises a compound offormula (I). For example, in some cases, the mixture of precursors areselected such that the ratio of the elements Li, S, P, and M result inthe formation of an ionically conductive compound described herein, suchas Li₂₀S₁₇MP₂, Li₂₁S_(17.5)SiP₂, Li₂₂S₁₈SiP₂, Li₂₄S₁₉MP₂, or Li₂₈S₂₁MP₂.Other suitable ratios for forming a compound as in formula (I) are alsopossible. For example, in certain cases, excess S may be present in themixture (e.g., sulfur in excess of that included in a formula of anionically conductive compound described herein). The excess S may, forexample, compensate for sulfur loss during mixing. For instance, in someembodiments, the mixture of precursors described herein has astoichiometric ratio of the elements Li_(2x), P_(2z), M_(y), and S_(d)where x, y, and z are as described above and d is greater than or equalto the sum of x+w+5z, where w is as described above.

For instance, in some embodiments d may be greater than or equal to 15,greater than or equal to 17, greater than or equal to 19, greater thanor equal to 21, greater than or equal to 23, greater than or equal to25, greater than or equal to 30, greater than or equal to 35, greaterthan or equal to 40, greater than or equal to 45, greater than or equalto 50, greater than or equal to 100, or greater than or equal to 150. Incertain embodiments, d may be less than or equal to 200, less than orequal to 100, less than or equal to 50, or less than or equal to 45.Combinations of the above referenced ranges are also possible (e.g.,greater than or equal to 15 and less than or equal to 200). Other rangesare also possible.

In some embodiments, the mixture of precursors comprise or consist of:Li₂S, MS₂ (e.g., SiS₂ or GeS₂) and P₂S₅; or Li₂S, M (e.g., Si or Ge), S₈and P₂S₅; or Li₂S, M (e.g., Si or Ge), S₈ and P.

The mixture of precursors (e.g., comprising a mixture of the elementsLi, S, P, and M) may be heated to any suitable temperature for forming acompound described herein. In certain embodiments, the mixture ofprecursors is heated to a temperature of greater than or equal to 400°C., greater than or equal to 450° C., greater than or equal to 500° C.,greater than or equal to 550° C., greater than or equal to 600° C.,greater than or equal to 650° C., greater than or equal to 700° C.,greater than or equal to 750° C., greater than or equal to 800° C., orgreater than or equal to 850° C. In some embodiments, the mixture ofprecursors is heated to a temperature less than or equal to 900° C.,less than or equal to 850° C., less than or equal to 800° C., less thanor equal to 750° C., less than or equal to 700° C., less than or equalto 650° C., less than or equal to 600° C., less than or equal to 550°C., less than or equal to 500° C., or less than or equal to 450° C.Combinations of the above-referenced ranges are also possible (e.g.,greater than or equal to 400° C. and less than or equal to 900° C.,greater than or equal to 400° C. and less than or equal to 800° C.,greater than or equal to 500° C. and less than or equal to 700° C.,greater than or equal to 600° C. and less than or equal to 800° C.).Other ranges are also possible.

The mixture of precursors may be heated for any suitable amount of time.In some cases, the mixture of precursors may be heated for greater thanor equal to 3 hours, greater than or equal to 5 hours, greater than orequal to 8 hours, greater than or equal to 12 hours, greater than orequal to 16 hours, or greater than or equal to 20 hours. In certainembodiments, the mixture of precursors is heated for less than or equalto 24 hours, less than or equal to 48 hours, less than or equal to 36hours, less than or equal to 24 hours, less than or equal to 20 hours,less than or equal to 16 hours, less than or equal to 12 hours, lessthan or equal to 8 hours, or less than or equal to 5 hours. Combinationsof the above referenced ranges are also possible (e.g., greater than orequal to 3 hours and less than or equal to 24 hours, greater than orequal to 5 hours and less than or equal to 12 hours, greater than orequal to 8 hours and less than or equal to 20 hours, greater than orequal to 12 hours and less than or equal to 24 hours). Other ranges arealso possible.

The mixture of precursors may be heated at any suitable pressure. Insome embodiments, the mixture of precursors are heated at a relativelylow pressure. For example, in certain embodiments, the mixture ofprecursors is heated at a pressure of between 0.1 MPa and 0.3 MPa, or atother suitable pressures.

In certain embodiments, after heating the mixture of precursors, themixture is cooled. For example, the mixture of precursors may be heatedto a temperature between 400° C. and 900° C. (e.g., between 400° C. and800° C.) for between 3 hours to 24 hours, and the mixture may be cooledto a temperature less than 400° C. such as room temperature. The mixturemay then be ground into a plurality of particles of desired size. Thoseskilled in the art would be capable of selecting suitable methods forgrinding a material into particles including, for example, ball millingor blender crushing. In some embodiments, the mixture of precursors maybe ground in a ball mill prior to and/or during heating. In some cases,the grinding of the plurality of particles is conducted at relative lowpressures. For example, the grinding of the plurality of particles maybe conducted at pressures less than or equal to about 1 GPa, less thanor equal to about 500 MPa, less than or equal to about 100 MPa, lessthan or equal to about 50 MPa, less than or equal to about 10 MPa, lessthan or equal to about 5 MPa, less than or equal to about 1 MPa, or lessthan or equal to about 0.5 MPa. In certain embodiments, the grinding ofthe plurality of particles may be conducted at pressures of at leastabout 0.1 MPa, at least about 0.5 MPa, at least about 1 MPa, at leastabout 5 MPa, at least about 10 MPa, at least about 50 MPa, at leastabout 100 MPa, or at least about 500 MPa. Combinations of theabove-referenced ranges are also possible (e.g., at least about 0.1 MPaand less than or equal to about 1 GPa). Other ranges are also possible.

In some embodiments, a compound described herein (e.g., the compound offormula (I)) is deposited as a layer. In certain embodiments, aplurality of particles comprising the compound of formula (I) aredeposited as a layer (e.g., in an electrochemical cell).

A layer comprising a compound described herein (e.g., the compound offormula (I)) may be deposited on a surface (e.g., on another layer) byany suitable method such as sputtering (e.g., magnetron sputtering), ionbeam deposition, molecular beam epitaxy, electron beam evaporation,vacuum thermal evaporation, aerosol deposition, sol-gel, laser ablation,chemical vapor deposition (CVD), thermal evaporation, plasma enhancedchemical vacuum deposition (PECVD), laser enhanced chemical vapordeposition, jet vapor deposition, etc. In some embodiments, a layercomprising a compound described herein is made by cold pressing. Thetechnique used may depend on the desired thickness of the layer, thematerial being deposited on, etc. The compound of formula (I) may bedeposited in powder form, in some cases. In some embodiments, theparticles comprising the compound of formula (I) may be deposited on asurface and sintered.

In some embodiments, the layer comprising the compound of formula (I) isdeposited on an electrode/electroactive material (e.g., an anode, acathode). In certain embodiments, the layer comprising the compound offormula (I) is deposited on a separator, a protective layer, anelectrolyte layer, or another layer of an electrochemical cell.

In certain embodiments, a layer comprising the compound of formula (I),or a plurality of particles comprising the compound of formula (I) asdescribed herein, is substantially crystalline. In some embodiments, thelayer comprising the compound of formula (I), or a plurality ofparticles comprising the compound of formula (I) as described herein, isat least partially amorphous. In certain embodiments, the layercomprising the compound of formula (I), or a plurality of particlescomprising the compound of formula (I) as described herein, is between 1wt. % and 100 wt. % crystalline. That is to say, in some embodiments,the crystalline fraction of the compound of formula (I) comprised by thelayer (or particles) is in the range of 1% to 100% based on the totalweight of the compound of formula (I) comprised by the layer (orparticles). In certain embodiments, the layer comprising the compound offormula (I), or a plurality of particles comprising the compound offormula (I) as described herein, is greater than or equal to 1 wt. %,greater than or equal to 2 wt. %, greater than or equal to 5 wt. %,greater than or equal to 10 wt. %, greater than or equal to 20 wt. %,greater than or equal to 25 wt. %, greater than or equal to 50 wt. %,greater than or equal to 75 wt. %, greater than or equal to 90 wt. %,greater than or equal to 95 wt. %, greater than or equal to 98 wt. %,greater than or equal to 99 wt. %, or greater than or equal to 99.9 wt.% crystalline. In certain embodiments, the layer comprising the compoundof formula (I), or a plurality of particles comprising the compound offormula (I) as described herein, is less than or equal to 99.9 wt. %,less than or equal to 98 wt. %, less than or equal to 95 wt. %, lessthan or equal to 90 wt. %, less than or equal to 75 wt. %, less than orequal to 50 wt. %, less than or equal to 25 wt. %, less than or equal to20 wt. %, less than or equal to 10 wt. %, less than or equal to 5 wt. %,or less than or equal to 2 wt. % crystalline.

In some embodiments, a layer comprising the compound of formula (I), ora plurality of particles comprising the compound of formula (I) asdescribed herein, is greater than or equal to 99.2 wt. %, greater thanor equal to 99.5 wt. %, greater than or equal to 99.8 wt. %, or greaterthan or equal to 99.9 wt. % crystalline. In some cases, a layercomprising the compound of formula (I), or a plurality of particlescomprising the compound of formula (I) as described herein, may be 100%crystalline. Combinations of the above referenced ranges are alsopossible (e.g., greater than or equal to 1 wt. % and less than or equalto 100 wt. %, greater than or equal to 50 wt. % and less than or equalto 100 wt. %).

In some embodiments, the compound of formula (I) has a cubic crystalstructure. Unless indicated otherwise, the crystal structure and/orpercent crystallinity as used herein is determined by x-ray diffractioncrystallography at a wavelength of 1.541 nm using a synchrotron ofparticles comprising the compound. In some instances, Raman spectroscopymay be used.

In some embodiments, the ionically conductive compound of formula (I)may be present in a layer (e.g., a separator, a protective layer) in anamount of at least about 1 wt %, at least about 2 wt %, at least about 5wt %, at least about 10 wt %, at least about 20 wt %, about 30 wt %, atleast about 40 wt %, at least about 50 wt %, at least about 60 wt %, atleast about 70 wt %, at least about 80 wt %, at least about 85 wt %, atleast about 90 wt %, at least about 95 wt %, or at least about 98 wt %versus the total layer weight. In certain embodiments, the ionicallyconductive compound of formula (I) is present in the layer in an amountof less than or equal to about 100 wt %, less than or equal to about 99wt %, less than or equal to about 98 wt %, less than or equal to about95 wt %, less than or equal to about 90 wt %, less than or equal toabout 85 wt %, less than or equal to about 80 wt %, less than or equalto about 70 wt %, less than or equal to about 60 wt %, less than orequal to about 50 wt %, less than or equal to about 40 wt %, less thanor equal to about 30 wt %, less than or equal to about 20 wt %, lessthan or equal to about 10 wt %, less than or equal to about 5 wt %, orless than or equal to about 2 wt % versus the total layer weight.Combinations of the above-referenced ranges are also possible (e.g., atleast about 1 wt % and less than or equal to about 100 wt %). Otherranges are also possible.

In some cases, the layer may comprise the ionically conductive compoundof formula (I) and one or more additional materials (e.g., polymers,metals, ceramics, ionically-conductive materials) as described in moredetail, below.

In some embodiments, one or more layers of an electrochemical cell maycomprise the ionically conductive compound of formula (I). In somecases, the compound in the one or more layers is in the form of aplurality of particles. In some embodiments, the layer comprising thecompound of formula (I) is in direct contact with an electrode (e.g., anelectroactive material of the electrode).

In certain embodiments, the layer comprising the compound of formula (I)may allow ions (e.g., electrochemically active ions, such as lithiumions) to pass through the layer but may substantially impede electronsfrom passing across the layer. By “substantially impedes”, in thiscontext, it is meant that in this embodiment the layer allows lithiumion flux greater than or equal to ten times greater than electronpassage. Advantageously, particles and layers described herein (e.g.,comprising the compound of formula (I)) may be capable of conductingspecific cations (e.g., lithium cations) while not conducting certainanions (e.g., polysulfide anions) and/or may be capable of acting as abarrier to an electrolyte and/or a component in the electrolyte (e.g., apolysulfide species) for the electrode.

In some embodiments, the layer (e.g., a separator, a protective layer, asolid electrolyte layer) comprising the ionically conductive compound offormula (I) is ionically conductive. In some embodiments, the averageionic conductivity of the layer comprising the ionically conductivecompound of formula (I) is greater than or equal to 10⁻⁵ S/cm, greaterthan or equal to 10⁻⁴ S/cm, greater than or equal to 10⁻³ S/cm, greaterthan or equal to 10⁻² S/cm, greater than or equal to 10⁻¹ S/cm. Incertain embodiments, the average ionic conductivity of the layercomprising the ionically conductive compound of formula (I) may be lessthan or equal to 1 S/cm, less than or equal to 10⁻¹ S/cm, less than orequal to 10⁻² S/cm, less than or equal to 10⁻³ S/cm, or less than orequal to 10⁻⁴ S/cm. Combinations of the above-referenced ranges are alsopossible (e.g., an average ionic conductivity of greater than or equalto 10⁻⁵ S/cm and less than or equal to 10⁻¹ S/cm). Other ionconductivities are also possible.

In some embodiments, the average ion conductivity of the layercomprising the ionically conductive compound of formula (I) can bedetermined by pressing the layer between two copper cylinders at apressure of up to 3 tons/cm². In certain embodiments, the average ionconductivity (i.e., the inverse of the average resistivity) can bemeasured at 500 kg/cm² increments using a conductivity bridge (i.e., animpedance measuring circuit) operating at 1 kHz. In some suchembodiments, the pressure is increased until changes in average ionconductivity are no longer observed in the sample. Conductivity may bemeasured at room temperature (e.g., 25 degrees Celsius).

As described herein, it may be desirable to determine if a layerincluding a compound described herein has advantageous properties ascompared to a layer formed of other materials for particularelectrochemical systems. Simple screening tests can be employed to helpselect between candidate materials. One simple screening test includespositioning a layer (e.g., comprising the compound of formula (I)) in anelectrochemical cell, e.g., as a protective layer in a cell. Theelectrochemical cell may then undergo multiple discharge/charge cycles,and the electrochemical cell may be observed for whether inhibitory orother destructive behavior occurs compared to that in a control system.If inhibitory or other destructive behavior is observed during cyclingof the cell, as compared to the control system, it may be indicative ofdegradation or other failure of the layer in question, within theassembled electrochemical cell. It is also possible to evaluate theelectrical conductivity and/or ion conductivity of the layer usingmethods described herein and known to one of ordinary skill in the art.The measured values may be compared to select between candidatematerials and may be used for comparison with baseline material(s) inthe control.

In some embodiments, it may be desirable to test the layer (e.g., alayer comprising the compound of formula (I)) for swelling in thepresence of a particular electrolyte or solvent to be used in anelectrochemical cell. A simple screening test may involve, for example,pieces of the layer that are weighed and then placed in a solvent or anelectrolyte to be used in an electrochemical cell for any suitableamount of time (e.g., 24 hours). The percent difference in weight (orvolume) of the layer before and after the addition of a solvent or anelectrolyte may determine the amount of swelling of the layer in thepresence of the electrolyte or the solvent.

Another simple screening test may involve determining the stability(i.e., integrity) of a layer (e.g., a layer comprising the compound offormula (I)) to polysulfides. Briefly, the layer may be exposed to apolysulfide solution/mixture for any suitable amount of time (e.g., 72hours) and the percent weight loss of the layer after exposure to thepolysulfide solution may be determined by calculating the difference inweight of the layer before and after the exposure. For example, in someembodiments, the percent weight loss of the layer after exposure to thepolysulfide solution may be less than or equal to 15 wt. %, less than orequal to 10 wt. %, less than or equal to 5 wt. %, less than or equal to2 wt. %, less than or equal to 1 wt. %, or less than or equal to 0.5 wt.%. In certain embodiments, the percent weight loss of the layer afterexposure to the polysulfide solution may be greater than or equal to 0.1wt. %, greater than or equal to 0.5 wt. %, greater than or equal to 1wt. %, greater than or equal to 2 wt. %, greater than or equal to 5 wt.%, or greater than or equal to 10 wt. %. Combinations of theabove-referenced ranges are also possible (e.g., greater than or equalto 0.1 wt. % and less than or equal to 5 wt. %).

Yet another simple screening test may involve determining the stability(i.e. integrity) of a layer (e.g., a layer comprising the compound offormula (I)) to metallic lithium. Briefly, a layer or a pelletcomprising the compound of formula (I) may be placed between two lithiummetal foils in an electrochemical cell and one can measure the change inimpedance over any suitable amount of time (e.g., 72 hours). In general,the lower impedance may result in a greater stability of the layer tometallic lithium.

The above described screening tests may also be adapted and used todetermine the properties of individual components of the layer (e.g., aplurality of particles comprising the compound of formula (I)).

Turning now to the figures, the various embodiments of the currentdisclosure are described in more detail below. It should be understoodthat while certain layers depicted in the figures are disposed directlyon one another, other intermediate layers may also be present betweenthe depicted layers in certain embodiments. Accordingly, as used herein,when a layer is referred to as being “disposed on”, “deposited on”, or“on” another layer, it can either be directly disposed on, depositedonto, or on the layer, or an intervening layer may also be present. Incontrast, a layer that is “directly disposed on”, “in contact with”,“directly deposited on”, or “directly on” another layer indicates thatno intervening layer is present.

In some embodiments, one or more ionically conductive compoundsdescribed herein may be incorporated into a separator (e.g., separator30 in FIG. 1A). Generally, a separator is interposed between a cathodeand an anode in an electrochemical cell. The separator may separate orinsulate the anode and the cathode from each other preventing shortcircuiting, and may permit the transport of ions between the anode andthe cathode. The separator may be porous, wherein the pores may bepartially or substantially filled with electrolyte. Separators may besupplied as porous free standing films which are interleaved with theanodes and the cathodes during the fabrication of cells. Alternatively,the separator layer may be applied directly to the surface of one of theelectrodes.

FIG. 1A shows an example of an article that can be incorporated into anelectrochemical cell. Article 10 includes an electrode 20 (e.g., ananode or a cathode) that comprises an electroactive material and aseparator 30 adjacent the electrode. In some embodiments, the separator(e.g., separator 30) comprises the ionically conductive compound offormula (I) and/or a plurality of particles comprising the ionicallyconductive compound of formula (I). However, other materials can also beused to form the separator. The electrode may include an electroactivematerial (e.g., an anode active electrode material, a cathode activeelectrode material), described in more detail below.

In some embodiments, the electrochemical cell comprises an electrolyte.In some embodiments, the separator is located between the electrolyteand an electrode (e.g., an anode, a cathode). For example, asillustrated in FIG. 1B, article 11 includes an electrode 20 (e.g., ananode or a cathode) that comprises an electroactive material, anelectrolyte 40 adjacent the electrode, and separator 30 adjacent theelectrolyte. The electrolyte can function as a medium for the storageand transport of ions. The electrolyte may have any suitableconfiguration such as a liquid electrolyte, a solid electrolyte, or agel polymer electrolyte, as described in more detail herein.

In some embodiments, the separator comprises a polymeric material (e.g.,polymeric material that does or does not swell upon exposure toelectrolyte). The separator may optionally include an ionicallyconductive compound (or plurality of particles comprising the compound)of formula (I). In certain embodiments, the ionically conductivecompound is directly deposited on at least a portion of a surface of theseparator. In certain embodiments, the ionically conductive compound isincorporated into the separator.

The separator can be configured to inhibit (e.g., prevent) physicalcontact between a first electrode and a second electrode, which couldresult in short circuiting of the electrochemical cell. The separatorcan be configured to be substantially electronically non-conductive,which can inhibit the degree to which the separator causes shortcircuiting of the electrochemical cell. In certain embodiments, all orportions of the separator can be formed of a material with a bulkelectronic resistivity of greater than or equal to 10⁴, greater than orequal to 10⁵, greater than or equal to 10¹⁰, greater than or equal to10¹⁵, or greater than or equal to 10²⁰ Ohm-meters. In some embodiments,the bulk electronic resistivity may be less than or equal to 10⁵⁰Ohm-meters. Bulk electronic resistivity may be measured at roomtemperature (e.g., 25 degrees Celsius).

In some embodiments, the separator can be a solid. The separator may beporous to allow an electrolyte solvent to pass through it. In somecases, the separator does not substantially include a solvent (like in agel), except for solvent that may pass through or reside in the pores ofthe separator. In other embodiments, a separator may be in the form of agel.

In some embodiments, the porosity of the separator can be, for example,greater than or equal to 30 vol %, greater than or equal to 40 vol %,greater than or equal to 50%, greater than or equal to 60 vol %, greaterthan or equal to 70 vol %, greater than or equal to 80 vol %, or greaterthan or equal to 90 vol %. In certain embodiments, the porosity is lessthan or equal to 90 vol %, less than or equal to 80 vol %, less than orequal to 70 vol %, less than or equal to 60 vol %, less than or equal to50 vol %, less than or equal to 40 vol %, or less than or equal to 30vol %. Other porosities are also possible. Combinations of theabove-noted ranges are also possible. Porosity as used herein refers tothe fraction of a volume of voids in a layer divided by the total volumeof the layer and is measured using mercury porosimetry.

A separator can be made of a variety of materials. In some embodiments,the separator comprises the ionically conductive compound of formula(I). Additional or alternatively, the separator may comprise a suitableseparator material such as a polymer material. Examples of suitablepolymer materials include, but are not limited to, polyolefins (e.g.,polyethylenes, poly(butene-1), poly(n-pentene-2), polypropylene,polytetrafluoroethylene), polyamines (e.g., poly(ethylene imine) andpolypropylene imine (PPI)); polyamides (e.g., polyamide (Nylon),poly(ϵ-caprolactam) (Nylon 6), poly(hexamethylene adipamide) (Nylon66)), polyimides (e.g., polyimide, polynitrile, andpoly(pyromellitimide-1,4-diphenyl ether) (Kapton®) (NOMEX®) (KEVLAR®));polyether ether ketone (PEEK); vinyl polymers (e.g., polyacrylamide,poly(2-vinyl pyridine), poly(N-vinylpyrrolidone),poly(methylcyanoacrylate), poly(ethylcyanoacrylate),poly(butylcyanoacrylate), poly(isobutylcyanoacrylate), poly(vinylacetate), poly (vinyl alcohol), poly(vinyl chloride), poly(vinylfluoride), poly(2-vinyl pyridine), vinyl polymer, polychlorotrifluoroethylene, and poly(isohexylcynaoacrylate)); polyacetals; polyesters(e.g., polycarbonate, polybutylene terephthalate, polyhydroxybutyrate);polyethers (poly(ethylene oxide) (PEO), poly(propylene oxide) (PPO),poly(tetramethylene oxide) (PTMO)); vinylidene polymers (e.g.,polyisobutylene, poly(methyl styrene), poly(methylmethacrylate) (PMMA),poly(vinylidene chloride), and poly(vinylidene fluoride)); polyaramides(e.g., poly(imino-1,3-phenylene iminoisophthaloyl) andpoly(imino-1,4-phenylene iminoterephthaloyl)); polyheteroaromaticcompounds (e.g., polybenzimidazole (PBI), polybenzobisoxazole (PBO) andpolybenzobisthiazole (PBT)); polyheterocyclic compounds (e.g.,polypyrrole); polyurethanes; phenolic polymers (e.g.,phenol-formaldehyde); polyalkynes (e.g., polyacetylene); polydienes(e.g., 1,2-polybutadiene, cis or trans-1,4-polybutadiene); polysiloxanes(e.g., poly(dimethylsiloxane) (PDMS), poly(diethylsiloxane) (PDES),polydiphenylsiloxane (PDPS), and polymethylphenylsiloxane (PMPS)); andinorganic polymers (e.g., polyphosphazene, polyphosphonate, polysilanes,polysilazanes). In some embodiments, the polymer may be selected frompoly(n-pentene-2), polypropylene, polytetrafluoroethylene, polyamides(e.g., polyamide (Nylon), poly(ϵ-caprolactam) (Nylon 6),poly(hexamethylene adipamide) (Nylon 66)), polyimides (e.g.,polynitrile, and poly(pyromellitimide-1,4-diphenyl ether) (Kapton®)(NOMEX®) (KEVLAR®)), polyether ether ketone (PEEK), and combinationsthereof.

The mechanical and electronic properties (e.g., conductivity,resistivity) of these polymers are known. Accordingly, those of ordinaryskill in the art can choose suitable materials based on their mechanicaland/or electronic properties (e.g., ionic and/or electronicconductivity/resistivity), and/or can modify such polymers to beionically conducting (e.g., conductive towards single ions) based onknowledge in the art, in combination with the description herein. Forexample, the polymer materials listed above and herein may furthercomprise salts, for example, lithium salts (e.g., LiSCN, LiBr, LiI,LiClO₄, LiAsF₆, LiSO₃CF₃, LiSO₃CH₃, LiBF₄, LiB(Ph)₄, LiPF₆,LiC(SO₂CF₃)₃, and LiN(SO₂CF₃)₂), and/or the ionically conductivecompound of formula (I) to enhance ionic conductivity, if desired.

The separator may be porous. In some embodiments, the separator poresize may be, for example, less than 5 microns. In some embodiments, thepore size may be less than or equal to 5 microns, less than or equal to3 microns, less than or equal to 2 microns, less than or equal to 1micron, less than or equal to 500 nm, less than or equal to 300 nm, lessthan or equal to 100 nm, or less than or equal to 50 nm. In someembodiments, the pore size may be greater than or equal to 50 nm,greater than or equal to 100 nm, greater than or equal to 300 nm,greater than or equal to 500 nm, or greater than or equal to 1 micron.Other values are also possible. Combinations of the above-noted rangesare also possible (e.g., a pore size of less than 300 nm and greaterthan or equal to 100 nm). In certain embodiments, the separator may besubstantially non-porous.

The separator may have any suitable thickness. In some embodiments, theseparator may have a thickness of greater than or equal to 500 nm,greater than or equal to 1 micron, greater than or equal to 5 microns,greater than or equal to 10 microns, greater than or equal to 15microns, greater than or equal to 20 microns, greater than or equal to25 microns, greater than or equal to 30 microns, or greater than orequal to 40 microns. In some embodiments, the thickness of the separatoris less than or equal to 50 microns, less than or equal to 40 microns,less than or equal to 30 microns, less than or equal to 20 microns, lessthan or equal to 10 microns, or less than or equal to 5 microns. Othervalues are also possible. Combinations of the above-noted ranges arealso possible.

The average thickness of the separator or other layers described hereinis determined by scanning electron microscopy (SEM). Briefly, the layercan be imaged along a cross-section (e.g., by cutting the layer) afterformation and the image may be acquired by SEM. The average thicknessmay be determined by taking an average of the thickness of the sample atseveral different locations along the cross-section (e.g., at least 10locations). Those skilled in the art would be capable of selecting anappropriate magnification for imaging the sample.

In certain embodiments, a protective layer may comprise the ionicallyconductive compound of formula (I) and/or a plurality of particlescomprising the ionically conductive compound of formula (I). In someembodiments, a protective layer that incorporates the ionicallyconductive compounds described herein is substantially impermeable tothe electrolyte. The protective layer may be configured such that it isunswollen in the presence of the electrolyte. However, in otherembodiments, at least a portion of the protective layer can be swollenin the presence of the electrolyte. The protective layer may, in somecases, be substantially non-porous. The protective layer may bepositioned directly adjacent an electrode, or adjacent the electrode viaan intervening layer (e.g., another protective layer). Referring now toFIG. 1C, in some embodiments, an article 12 comprises electrode 20, aprotective layer 32 disposed on or adjacent at least a portion ofelectrode active surface 20′, and an optional electrolyte 40. In otherembodiments, a second protective layer (not shown in FIG. 1C) adjacentprotective layer 32 may be present. In some embodiments, at least one orboth of protective layer 32 and the second protective layer includes anion-conductive layer comprising the ionically conductive compound offormula (I). Other configurations are also possible.

Although in some embodiments the protective layer is an ion-conductivelayer comprising the ionically conductive compound of formula (I), othermaterials may also be used in addition to, or alternatively to, thecompound of formula (I) to form the protective layer. Additionally,where more than one protective layer may be present, each of the layersmay independently formed of one or more materials described herein. Insome embodiments, the protective layer comprises a ceramic and/or aglass (e.g., an ion conducting ceramic/glass conductive to lithiumions). Suitable glasses and/or ceramics include, but are not limited to,those that may be characterized as containing a “modifier” portion and a“network” portion, as known in the art. The modifier may include a metaloxide of the metal ion conductive in the glass or ceramic. The networkportion may include a metal chalcogenide such as, for example, a metaloxide or sulfide. For lithium metal and other lithium-containingelectrodes, an ion conductive layer may be lithiated or contain lithiumto allow passage of lithium ions across it. Ion conductive layers mayinclude layers comprising a material such as lithium nitrides, lithiumsilicates, lithium borates, lithium aluminates, lithium phosphates,lithium phosphorus oxynitrides, lithium silicosulfides, lithiumgermanosulfides, lithium oxides (e.g., Li₂O, LiO, LiO₂, LiRO₂, where Ris a rare earth metal), lithium lanthanum oxides, lithium lanthanumzirconium oxides, lithium titanium oxides, lithium borosulfides, lithiumaluminosulfides, lithium phosphates, and lithium phosphosulfides, andcombinations thereof. The selection of the material will be dependent ona number of factors including, but not limited to, the properties ofelectrolyte, anode, and cathode used in the cell.

In one set of embodiments, the protective layer is a non-electroactivemetal layer. The non-electroactive metal layer may comprise a metalalloy layer, e.g., a lithiated metal layer especially in the case wherea lithium anode is employed. The lithium content of the metal alloylayer may vary from 0.5% by weight to 20% by weight, depending, forexample, on the specific choice of metal, the desired lithium ionconductivity, and the desired flexibility of the metal alloy layer.Suitable metals for use in the ion conductive material include, but arenot limited to, Al, Zn, Mg, Ag, Pb, Cd, Bi, Ga, In, Ge, Sb, As, and Sn.Sometimes, a combination of metals, such as the ones listed above, maybe used in an ion conductive material.

The protective layer may have any suitable thickness. In someembodiments, the protective layer described herein may have a thicknessof greater than or equal to 1 nm, greater than or equal to 2 nm, greaterthan or equal to 5 nm, greater than or equal to 10 nm, greater than orequal to 20 nm, greater than or equal to 50 nm, greater than or equal to100 nm, greater than or equal to 500 nm, greater than or equal to 1micron, greater than or equal to 2 microns, or greater than or equal to5 microns. In certain embodiments, the protective layer may have athickness of less than or equal to 10 microns, less than or equal to 5microns, less than or equal to 2 microns, less than or equal to 1micron, less than or equal to 500 nm, less than or equal to 100 nm, lessthan or equal to 50 nm, less than or equal to 20 nm, less than or equalto 10 nm, less than or equal to 5 nm, or less than or equal to 2 nm.Other values are also possible. Combinations of the above-noted rangesare also possible.

In some embodiments, the protective layer is a polymer layer or a layerthat comprises a polymeric material. In some embodiments, the ionicallyconductive compound of formula (I) is incorporated into the polymerlayer. Suitable polymer layers for use in electrochemical cells may be,for example, highly conductive towards lithium and minimally conductivetowards electrons. Such polymers may include, for example, ionicallyconductive polymers, sulfonated polymers, and hydrocarbon polymers. Theselection of the polymer will be dependent upon a number of factorsincluding the properties of electrolyte, anode, and cathode used in thecell. Suitable ionically conductive polymers include, e.g., ionicallyconductive polymers known to be useful in solid polymer electrolytes andgel polymer electrolytes for lithium electrochemical cells, such as, forexample, polyethylene oxides. Suitable sulfonated polymers include,e.g., sulfonated siloxane polymers, sulfonatedpolystyrene-ethylene-butylene polymers, and sulfonated polystyrenepolymers. Suitable hydrocarbon polymers include, e.g.,ethylene-propylene polymers, polystyrene polymers, and the like.

Polymer layers can also include crosslinked polymer materials formedfrom the polymerization of monomers such as alkyl acrylates, glycolacrylates, polyglycol acrylates, polyglycol vinyl ethers, and polyglycoldivinyl ethers. For example, one such crosslinked polymer material ispolydivinyl poly(ethylene glycol). The crosslinked polymer materials mayfurther comprise salts, for example, lithium salts, to enhance ionicconductivity. In one embodiment, the polymer layer comprises acrosslinked polymer.

Other classes polymers that may be suitable for use in a polymer layerinclude, but are not limited to, polyamines (e.g., poly(ethylene imine)and polypropylene imine (PPI)); polyamides (e.g., polyamide (Nylon),poly(ϵ-caprolactam) (Nylon 6), poly(hexamethylene adipamide) (Nylon66)), polyimides (e.g., polyimide, polynitrile, andpoly(pyromellitimide-1,4-diphenyl ether) (Kapton)); vinyl polymers(e.g., polyacrylamide, poly(2-vinyl pyridine), poly(N-vinylpyrrolidone),poly(methylcyanoacrylate), poly(ethylcyanoacrylate),poly(butylcyanoacrylate), poly(isobutylcyanoacrylate), poly(vinylacetate), poly (vinyl alcohol), poly(vinyl chloride), poly(vinylfluoride), poly(2-vinyl pyridine), vinyl polymer, polychlorotrifluoroethylene, and poly(isohexylcynaoacrylate)); polyacetals; polyolefins(e.g., poly(butene-1), poly(n-pentene-2), polypropylene,polytetrafluoroethylene); polyesters (e.g., polycarbonate, polybutyleneterephthalate, polyhydroxybutyrate); polyethers (poly(ethylene oxide)(PEO), poly(propylene oxide) (PPO), poly(tetramethylene oxide) (PTMO));vinylidene polymers (e.g., polyisobutylene, poly(methyl styrene),poly(methylmethacrylate) (PMMA), poly(vinylidene chloride), andpoly(vinylidene fluoride)); polyaramides (e.g., poly(imino-1,3-phenyleneiminoisophthaloyl) and poly(imino-1,4-phenylene iminoterephthaloyl));polyheteroaromatic compounds (e.g., polybenzimidazole (PBI),polybenzobisoxazole (PBO) and polybenzobisthiazole (PBT));polyheterocyclic compounds (e.g., polypyrrole); polyurethanes; phenolicpolymers (e.g., phenol-formaldehyde); polyalkynes (e.g., polyacetylene);polydienes (e.g., 1,2-polybutadiene, cis or trans-1,4-polybutadiene);polysiloxanes (e.g., poly(dimethylsiloxane) (PDMS),poly(diethylsiloxane) (PDES), polydiphenylsiloxane (PDPS), andpolymethylphenylsiloxane (PMPS)); and inorganic polymers (e.g.,polyphosphazene, polyphosphonate, polysilanes, polysilazanes). Themechanical and electronic properties (e.g., conductivity, resistivity)of these polymers are known. Accordingly, those of ordinary skill in theart can choose suitable polymers for use in lithium batteries, e.g.,based on their mechanical and/or electronic properties (e.g., ionicand/or electronic conductivity), and/or can modify such polymers to beionically conducting (e.g., conductive towards single ions) and/orelectronically conducting based on knowledge in the art, in combinationwith the description herein. For example, the polymer materials listedabove may further comprise salts, for example, lithium salts (e.g.,LiSCN, LiBr, LiI, LiClO₄, LiAsF₆, LiSO₃CF₃, LiSO₃CH₃, LiBF₄, LiB(Ph)₄,LiPF₆, LiC(SO₂CF₃)₃, and LiN(SO₂CF₃)₂), to enhance ionic conductivity.

The polymeric materials can be selected or formulated to have suitablephysical/mechanical characteristics by, for example, tailoring theamounts of components of polymer blends, adjusting the degree ofcross-linking (if any), etc.

In some embodiments, a composite layer comprises a polymer material andan ionically conductive compound described herein (e.g., an ionicallyconductive compound of formula (I)). Such a composite layer may beformed by any suitable method including, for example: co-spraying (e.g.,via aerosol deposition) the polymer material and the ionicallyconductive compound of formula (I) onto a substrate; casting thecomposite layer from a slurry, solution, or suspension comprising thepolymer material and the ionically conductive compound of formula (I);pressing particles comprising the ionically conductive compound offormula (I) into a polymer layer comprising a polymer material; and/orfilling pores of a layer comprising the ionically conductive compound offormula (I) with a polymer material. Other methods for forming compositelayers are also possible and are generally known in the art. Thecomposite layer may be used for any suitable component of anelectrochemical cell described herein, such as a protective layer. Theseand other methods for forming such composite layers are described inmore detail in U.S. Provisional Patent Application No. 62/164,200, filedMay 20, 2015 and entitled “Protective Layers for Electrodes,” which isincorporated herein by reference in its entirety.

As described herein, in certain embodiments, the electrochemical cellcomprises an electrolyte (e.g., electrolyte 40 in FIGS. 1B-1C). Theelectrolytes used in electrochemical or battery cells can function as amedium for the storage and transport of ions, and in the special case ofsolid electrolytes and gel electrolytes, these materials mayadditionally function as a separator between the anode and the cathode.Any suitable liquid, solid, or gel material capable of storing andtransporting ions may be used, so long as the material facilitates thetransport of ions (e.g., lithium ions) between the anode and thecathode. The electrolyte may be electronically non-conductive to preventshort circuiting between the anode and the cathode. In some embodiments,the electrolyte may comprise a non-solid electrolyte.

In some embodiments, an electrolyte is in the form of a layer having aparticular thickness. An electrolyte layer may have a thickness of, forexample, greater than or equal to 1 micron, greater than or equal to 5microns, greater than or equal to 10 microns, greater than or equal to15 microns, greater than or equal to 20 microns, greater than or equalto 25 microns, greater than or equal to 30 microns, greater than orequal to 40 microns, greater than or equal to 50 microns, greater thanor equal to 70 microns, greater than or equal to 100 microns, greaterthan or equal to 200 microns, greater than or equal to 500 microns, orgreater than or equal to 1 mm. In some embodiments, the thickness of theelectrolyte layer is less than or equal to 1 mm, less than or equal to500 microns, less than or equal to 200 microns, less than or equal to100 microns, less than or equal to 70 microns, less than or equal to 50microns, less than or equal to 40 microns, less than or equal to 30microns, less than or equal to 20 microns, less than or equal to 10microns, or less than or equal to 50 microns. Other values are alsopossible. Combinations of the above-noted ranges are also possible.

In some embodiments, the electrolyte includes a non-aqueous electrolyte.Suitable non-aqueous electrolytes may include organic electrolytes suchas liquid electrolytes, gel polymer electrolytes, and solid polymerelectrolytes. These electrolytes may optionally include one or moreionic electrolyte salts (e.g., to provide or enhance ionic conductivity)as described herein. Examples of useful non-aqueous liquid electrolytesolvents include, but are not limited to, non-aqueous organic solvents,such as, for example, N-methyl acetamide, acetonitrile, acetals, ketals,esters (e.g., esters of carbonic acid), carbonates (e.g., ethylenecarbonate, dimethyl carbonate), sulfones, sulfites, sulfolanes,suflonimidies (e.g., bis(trifluoromethane)sulfonimide lithium salt),aliphatic ethers, acyclic ethers, cyclic ethers, glymes, polyethers,phosphate esters (e.g., hexafluorophosphate), siloxanes, dioxolanes,N-alkylpyrrolidones, nitrate containing compounds, substituted forms ofthe foregoing, and blends thereof. Examples of acyclic ethers that maybe used include, but are not limited to, diethyl ether, dipropyl ether,dibutyl ether, dimethoxymethane, trimethoxymethane, 1,2-dimethoxyethane,diethoxyethane, 1,2-dimethoxypropane, and 1,3-dimethoxypropane. Examplesof cyclic ethers that may be used include, but are not limited to,tetrahydrofuran, tetrahydropyran, 2-methyltetrahydrofuran, 1,4-dioxane,1,3-dioxolane, and trioxane. Examples of polyethers that may be usedinclude, but are not limited to, diethylene glycol dimethyl ether(diglyme), triethylene glycol dimethyl ether (triglyme), tetraethyleneglycol dimethyl ether (tetraglyme), higher glymes, ethylene glycoldivinyl ether, diethylene glycol divinyl ether, triethylene glycoldivinyl ether, dipropylene glycol dimethyl ether, and butylene glycolethers. Examples of sulfones that may be used include, but are notlimited to, sulfolane, 3-methyl sulfolane, and 3-sulfolene. Fluorinatedderivatives of the foregoing are also useful as liquid electrolytesolvents.

In some cases, mixtures of the solvents described herein may also beused. For example, in some embodiments, mixtures of solvents areselected from the group consisting of 1,3-dioxolane and dimethoxyethane,1,3-dioxolane and diethyleneglycol dimethyl ether, 1,3-dioxolane andtriethyleneglycol dimethyl ether, and 1,3-dioxolane and sulfolane. Theweight ratio of the two solvents in the mixtures may range, in somecases, from 5 wt. %:95 wt. % to 95 wt. %:5 wt. %.

Non-limiting examples of suitable gel polymer electrolytes includepolyethylene oxides, polypropylene oxides, polyacrylonitriles,polysiloxanes, polyimides, polyphosphazenes, polyethers, sulfonatedpolyimides, perfluorinated membranes (NAFION resins), polydivinylpolyethylene glycols, polyethylene glycol diacrylates, polyethyleneglycol dimethacrylates, derivatives of the foregoing, copolymers of theforegoing, cross-linked and network structures of the foregoing, andblends of the foregoing.

In some embodiments, the non-aqueous electrolyte comprises at least onelithium salt. For example, in some cases, the at least one lithium saltis selected from the group consisting of LiNO₃, LiPF₆, LiBF₄, LiClO₄,LiAsF₆, Li₂SiF₆, LiSbF₆, LiAlCl₄, lithium bis-oxalatoborate, LiCF₃SO₃,LiN(SO₂F)₂, LiC(C_(n)F_(2n+1)SO₂)₃, wherein n is an integer in the rangeof from 1 to 20, and (C_(n)F_(2n+1)SO₂)_(m)QLi with n being an integerin the range of from 1 to 20, m being 1 when Q is selected from oxygenor sulfur, m being 2 when X is selected from nitrogen or phosphorus, andm being 3 when Q is selected from carbon or silicon.

In some cases, the electrolyte is a solid electrolyte layer comprisingthe ionically conductive compound of formula (I). Referring to FIG. 1D,in some embodiments, article 13 comprises electrode 20 (e.g., an anodeor a cathode) and a solid electrolyte 42 in direct contact withelectrode 20. In certain embodiments, as illustrated in FIG. 1E, article14 comprises electrode 20 (e.g., a cathode) and electrode 22 (e.g., ananode) in direct contact with solid electrolyte 42 at a first electrodesurface 20′ and a second electrode surface 22′, respectively. The solidelectrolyte may, for example, replace an organic or non-aqueous liquidelectrolyte in an electrochemical cell.

Non-limiting examples of other materials that may be suitable for asolid polymer electrolyte include polyethers, polyethylene oxides,polypropylene oxides, polyimides, polyphosphazenes, polyacrylonitriles,polysiloxanes, derivatives of the foregoing, copolymers of theforegoing, cross-linked and network structures of the foregoing, andblends of the foregoing.

A solid electrolyte layer (e.g., a solid electrolyte layer comprisingthe ionically conductive compound of formula (I)) may have any suitablethickness. For example, in some embodiments, the solid electrolyte layerhas a thickness of greater than or equal to 5 nm, greater than or equalto 10 nm, greater than or equal to 20 nm, greater than or equal to 50nm, greater than or equal to 100 nm, greater than or equal to 200 nm,greater than or equal to 500 nm, greater than or equal to 1 micron,greater than or equal to 5 microns, greater than or equal to 10 microns,greater than or equal to 15 microns, greater than or equal to 20microns, greater than or equal to 25 microns, greater than or equal to30 microns, or greater than or equal to 40 microns. In some embodiments,the thickness of the solid electrolyte layer is less than or equal to 50microns, less than or equal to 40 microns, less than or equal to 30microns, less than or equal to 20 microns, less than or equal to 10microns, less than or equal to 5 microns, less than or equal to 1micron, less than or equal to 500 nm, less than or equal to 200 nm, lessthan or equal to 100 nm, less than or equal to 50 nm, less than or equalto 20 nm, or less than or equal to 10 nm. Other values are alsopossible. Combinations of the above-noted ranges are also possible(e.g., greater than or equal to 10 nm and less than or equal to 50microns, greater than or equal to 10 nm and less than or equal to 1microns, greater than or equal to 100 nm and less than or equal to 2microns, greater than or equal to 500 nm and less than or equal to 10microns, greater than or equal to 1 micron and less than or equal to 25microns, greater than or equal to 15 microns and less than or equal to40 microns, greater than or equal to 25 microns and less than or equalto 50 microns).

In some embodiments, an electrode described herein may be a cathode(e.g., a cathode of an electrochemical cell). In some embodiments, anelectrode such as a cathode comprises the compound of formula (I). Insome embodiments, a layer comprising the compound of formula (I) isdeposited on a cathode, as described herein. In certain embodiments, thecompound of formula (I) is incorporated into the cathode (e.g., bymixing with a cathode active electrode material prior to the formationof the cathode).

In some embodiments, the electroactive material in the cathode comprisesthe compound of formula (I). That is, the ionically conductive compoundof formula (I) may be the active electrode species of the cathode. Incertain embodiments, the compound of formula (I) is a lithiumintercalation compound (e.g., a compound that is capable of reversiblyinserting lithium ions at lattice sites and/or interstitial sites). Insome embodiments, the cathode may be an intercalation electrodecomprising the ionically conductive compound of formula (I). In anexemplary embodiment, the cathode comprises Li₁₆S₁₅MP₂. In anotherexemplary embodiment, the cathode comprises Li₂₀S₁₇MP₂. In anotherexemplary embodiment, the cathode comprises Li₂₁S_(17.5)SiP₂. In yetanother exemplary embodiment, the cathode comprises Li₂₂S₁₈SiP₂. In yetanother exemplary embodiment, the cathode comprises Li₂₄S₁₉MP₂.Incorporation of other ionically conductive compounds in addition to oralternatively to those described above are also possible.

In some embodiments, the electroactive material in the cathodecomprising the compound of formula (I) is present in the cathode in anamount of at least about 30 wt %, at least about 40 wt %, at least about50 wt %, at least about 60 wt %, at least about 70 wt %, at least about80 wt %, at least about 85 wt %, at least about 90 wt %, at least about95 wt %, or at least about 98 wt % versus the total cathode weight. Incertain embodiments, the electroactive material in the cathodecomprising the compound of formula (I) is present in the cathode in anamount of less than or equal to about 100 wt %, less than or equal toabout 99 wt %, less than or equal to about 98 wt %, less than or equalto about 95 wt %, less than or equal to about 90 wt %, less than orequal to about 85 wt %, less than or equal to about 80 wt %, less thanor equal to about 70 wt %, less than or equal to about 60 wt %, or lessthan or equal to about 50 wt % versus the total cathode weight.Combinations of the above-referenced ranges are also possible (e.g., atleast about 40 wt % and less than or equal to about 95 wt %). Otherranges are also possible.

Additional non-limiting examples of suitable materials that mayintercalate ions of an electroactive material (e.g., alkaline metalions), and which may be included in an electrode (e.g., cathode),include oxides, titanium sulfide, and iron sulfide. Specific examplesinclude LixCoO₂, Li_(x)NiO₂, LixMnO₂, LixMn₂O₄, Li_(x)FePO₄,Li_(x)CoPO₄, Li_(x)MnPO₄, and Li_(x)NiPO₄, where (0<x≤1), andLiNi_(x)Mn_(y)Co_(z)O₂ where (x+y+z=1).

In some embodiments, active electrode materials for use as cathodeactive material in the cathode of the electrochemical cells describedherein may include, but are not limited to, electroactive transitionmetal chalcogenides, electroactive conductive polymers, sulfur, carbon,and/or combinations thereof. As used herein, the term “chalcogenides”pertains to compounds that contain one or more of the elements ofoxygen, sulfur, and selenium. Examples of suitable transition metalchalcogenides include, but are not limited to, the electroactive oxides,sulfides, and selenides of transition metals selected from the groupconsisting of Mn, V, Cr, Ti, Fe, Co, Ni, Cu, Y, Zr, Nb, Mo, Ru, Rh, Pd,Ag, Hf, Ta, W, Re, Os, and Ir. In one embodiment, the transition metalchalcogenide is selected from the group consisting of the electroactiveoxides of nickel, manganese, cobalt, and vanadium, and the electroactivesulfides of iron. In certain embodiments, the cathode may include as anelectroactive species elemental sulfur, sulfides, and/or polysulfides.

In one embodiment, a cathode includes one or more of the followingmaterials: manganese dioxide, iodine, silver chromate, silver oxide andvanadium pentoxide, copper oxide, copper oxyphosphate, lead sulfide,copper sulfide, iron sulfide, lead bismuthate, bismuth trioxide, cobaltdioxide, copper chloride, manganese dioxide, and carbon. In anotherembodiment, the cathode active layer comprises an electroactiveconductive polymer. Examples of suitable electroactive conductivepolymers include, but are not limited to, electroactive andelectronically conductive polymers selected from the group consisting ofpolypyrroles, polyanilines, polyphenylenes, polythiophenes, andpolyacetylenes. Examples of conductive polymers include polypyrroles,polyanilines, and polyacetylenes.

In some embodiments, active electrode materials for use as cathodeactive materials in electrochemical cells described herein includeelectroactive sulfur-containing materials (e.g., lithium-sulfurelectrochemical cells). “Electroactive sulfur-containing materials,” asused herein, relates to cathode active materials which comprise theelement sulfur in any form, wherein the electrochemical activityinvolves the oxidation or reduction of sulfur atoms or moieties. Thenature of the electroactive sulfur-containing materials useful in thepractice of this invention may vary widely, as known in the art. Forexample, in one embodiment, the electroactive sulfur-containing materialcomprises elemental sulfur. In another embodiment, the electroactivesulfur-containing material comprises a mixture of elemental sulfur and asulfur-containing polymer. Thus, suitable electroactivesulfur-containing materials may include, but are not limited to,elemental sulfur and organic materials comprising sulfur atoms andcarbon atoms, which may or may not be polymeric. Suitable organicmaterials include those further comprising heteroatoms, conductivepolymer segments, composites, and conductive polymers.

In certain embodiments, the sulfur-containing material (e.g., in anoxidized form) comprises a polysulfide moiety, S_(m), selected from thegroup consisting of covalent S_(m) moieties, ionic S_(m) moieties, andionic S_(m2—) moieties, wherein m is an integer equal to or greater than3. In some embodiments, m of the polysulfide moiety S_(m) of thesulfur-containing polymer is an integer equal to or greater than 6 or aninteger equal to or greater than 8. In some cases, the sulfur-containingmaterial may be a sulfur-containing polymer. In some embodiments, thesulfur-containing polymer has a polymer backbone chain and thepolysulfide moiety S_(m) is covalently bonded by one or both of itsterminal sulfur atoms as a side group to the polymer backbone chain. Incertain embodiments, the sulfur-containing polymer has a polymerbackbone chain and the polysulfide moiety S_(m) is incorporated into thepolymer backbone chain by covalent bonding of the terminal sulfur atomsof the polysulfide moiety.

In some embodiments, the electroactive sulfur-containing materialcomprises more than 50% by weight of sulfur. In certain embodiments, theelectroactive sulfur-containing material comprises more than 75% byweight of sulfur (e.g., more than 90% by weight of sulfur).

As will be known by those skilled in the art, the nature of theelectroactive sulfur-containing materials described herein may varywidely. In some embodiments, the electroactive sulfur-containingmaterial comprises elemental sulfur. In certain embodiments, theelectroactive sulfur-containing material comprises a mixture ofelemental sulfur and a sulfur-containing polymer.

In certain embodiments, an electrochemical cell as described hereincomprises one or more cathodes comprising sulfur as a cathode activematerial. In some such embodiments, the cathode includes elementalsulfur as a cathode active material. In some embodiments, the compoundof formula (I) is chosen such that the compound of formula (I) isdifferent from the anode active material and different from the cathodeactive material.

As described herein, an electrochemical cell or an article for use in anelectrochemical cell may include an electrode (e.g., an anode)comprising an anode active material. In some embodiments, a layercomprising the compound of formula (I) is deposited on an anode. Incertain embodiments, the compound of formula (I) is incorporated intothe electrode (e.g., by mixing with an active electrode material priorto the formation of the anode).

In some embodiments, the compound of formula (I) is present in the anodein an amount of at least about 40 wt %, at least about 50 wt %, at leastabout 60 wt %, at least about 70 wt %, at least about 80 wt %, or atleast about 85 wt % versus the total anode weight. In certainembodiments, the compound of formula (I) is present in the anode in anamount of less than or equal to about 90 wt %, less than or equal toabout 85 wt %, less than or equal to about 80 wt %, less than or equalto about 70 wt %, less than or equal to about 60 wt %, or less than orequal to about 50 wt % versus the total anode weight. Combinations ofthe above-referenced ranges are also possible (e.g., at least about 40wt % and less than or equal to about 90 wt %). Other ranges are alsopossible. In some embodiments, the total anode weight may be measured asthe anode active layer itself or the anode active material including anyprotective layer(s).

Suitable active electrode materials for use as anode active material inthe electrochemical cells described herein include, but are not limitedto, lithium metal such as lithium foil and lithium deposited onto aconductive substrate, lithium alloys (e.g., lithium-aluminum alloys andlithium-tin alloys), and graphite. Lithium can be contained as one filmor as several films, optionally separated by a protective material suchas a ceramic material or an ion conductive material described herein.Suitable ceramic materials include silica, alumina, or lithiumcontaining glassy materials such as lithium phosphates, lithiumaluminates, lithium silicates, lithium phosphorous oxynitrides, lithiumtantalum oxide, lithium aluminosulfides, lithium titanium oxides,lithium silcosulfides, lithium germanosulfides, lithium aluminosulfides,lithium borosulfides, and lithium phosphosulfides, and combinations oftwo or more of the preceding. Suitable lithium alloys for use in theembodiments described herein can include alloys of lithium and aluminum,magnesium, silicium (silicon), indium, and/or tin. While these materialsmay be preferred in some embodiments, other cell chemistries are alsocontemplated. For instance, in some embodiments, certain electrodes(e.g., anodes) may include other alkali metals (e.g., group 1 atoms) insome instances. In some embodiments, the anode may comprise one or morebinder materials (e.g., polymers, etc.).

In other embodiments, a silicon-containing or silicon-based anode may beused.

In some embodiments, the thickness of the anode may vary from, e.g., 2to 200 microns. For instance, the anode may have a thickness of lessthan 200 microns, less than 100 microns, less than 50 microns, less than25 microns, less than 10 microns, or less than 5 microns. In certainembodiments, the anode may have a thickness of greater than or equal to2 microns, greater than or equal to 5 microns, greater than or equal to10 microns, greater than or equal to 25 microns, greater than or equalto 50 microns, greater than or equal to 100 microns, or greater than orequal to 150 microns. Combinations of the above-referenced ranges arealso possible (e.g., greater than or equal to 2 microns and less than orequal to 200 microns, greater than or equal to 2 microns and less thanor equal to 100 microns, greater than or equal to 5 microns and lessthan or equal to 50 microns, greater than or equal to 5 microns and lessthan or equal to 25 microns, greater than or equal to 10 microns andless than or equal to 25 microns). Other ranges are also possible. Thechoice of the thickness may depend on cell design parameters such as theexcess amount of lithium desired, cycle life, and the thickness of thecathode electrode.

In some embodiments, an electrochemical cell described herein comprisesat least one current collector. Materials for the current collector maybe selected, in some cases, from metals (e.g., copper, nickel, aluminum,passivated metals, and other appropriate metals), metallized polymers,electrically conductive polymers, polymers comprising conductiveparticles dispersed therein, and other appropriate materials. In certainembodiments, the current collector is deposited onto the electrode layerusing physical vapor deposition, chemical vapor deposition,electrochemical deposition, sputtering, doctor blading, flashevaporation, or any other appropriate deposition technique for theselected material. In some cases, the current collector may be formedseparately and bonded to the electrode structure. It should beappreciated, however, that in some embodiments a current collectorseparate from the electroactive layer may not be present or needed.

In some embodiments, an electrochemical cell comprises a lithium orsilicon based anode, a cathode (e.g., a cathode comprising electroactivesulfur-containing material, an intercalation cathode) and a solidelectrolyte layer comprising the compound of formula (I). Theelectrochemical cell may include other components as described herein.

In certain embodiments, an electrochemical cell comprises a lithium orsilicon based anode, a cathode (e.g., a cathode comprising electroactivesulfur-containing material, an intercalation cathode), a liquidelectrolyte, and a protective layer comprising the compound of formula(I). The electrochemical cell may include other components as describedherein.

In some embodiments, an electrochemical cell comprises a lithium orsilicon based anode, a cathode (e.g., a cathode comprising electroactivesulfur-containing material, an intercalation cathode), a liquidelectrolyte, and a separator comprising the compound of formula (I). Theelectrochemical cell may include other components as described herein.

In certain embodiments, an electrochemical cell comprises a lithium orsilicon based anode, an intercalated cathode (e.g., a cathode comprisingthe compound of formula (I) as an intercalation species), and anelectrolyte (e.g., a liquid electrolyte). The electrochemical cell mayinclude other components as described herein.

The following examples are intended to illustrate certain embodiments ofthe present invention, but do not exemplify the full scope of theinvention.

Example 1

This example describes the conductivity and composition of variousionically conductive compounds having the formula as in Formula (I):Li_(2x)S_(x+w+5z)M_(y)P_(2z), where x is 5-14, y and z are 0.5-1, w isy, 1.5y, or 2y, and M is Si. A comparative compound, Li_(2x)S_(x+7)GeP₂,was also formed.

Ionically conductive compounds were formed by mixing of Li₂S, SiS₂ (orGeS₂), P₂S₅ or using different precursors like Li₂S, Si (or Ge), S₈,P₂S₅, or Li₂S, Si, S₈, P according to stoichiometry to form thecompounds as listed in Table 1. The mixtures were mixed by ball milling.The mixtures were sealed in a closed vessel under inert atmosphere(e.g., Argon) and heated to 700° C. for between 12-16 hours. The vesselswere then cooled to room temperature and the materials were ground intopowder form.

FIG. 2 shows the conductivity of particles of ionically conductivecompounds having the formula Li_(2x)S_(x+7)SiP₂ and is summarized inTable 1. Table 1 also includes particles of comparative compound,Li₂₄GeP₂S₁₉. The average ionic conductivity was measured by pressing theparticles between two copper cylinders at a pressure of up to 4tons/cm², and determining the conductivity using a conductivity bridgeoperating at 1 kHz at 25° C., at 500 kg/cm² increments of pressure untilchanges in average ion conductivity were no longer observed in thesample.

TABLE 1 x [S/cm] Li₁₀S₁₂SiP₂ 5 6.76 × 10⁻⁴  Li₁₂S₁₃SiP₂ 6 8.0 × 10⁻⁴Li₁₆S₁₅SiP₂ 8 1.9 × 10⁻³ Li₂₀S₁₇SiP₂ 10 2.93 × 10⁻³  Li₂₁S₁₇Si₂P 10.5  2 × 10⁻³ Li₂₁S_(17.5)SiP₂ 10.5 2.30 × 10⁻³  Li₂₂S₁₈SiP₂ 11 3.2 × 10⁻³Li₂₄S₁₉SiP₂ 12 2.83 × 10⁻³  Li₂₈S₂₁SiP₂ 14 2.2 × 10⁻³ Li₂₄S₁₉GeP₂ 12 3.1× 10⁻³

The XRD patterns indicate that the particles of Li₂₀SiP₂S₁₇ (FIG. 3) andLi₂₄SiP₂S₁₉ (FIG. 4) particles have different structures from that ofLi₁₀SnP₂S₁₂ particles. Li₂₀SiP₂S₁₇ and Li₂₄SiP₂S₁₉ had similar XRDpatterns, which showed much less pronounced satellite peaks, suggestingthat these structures have higher ordering (e.g., each having a cubiclattice) and higher degree of crystallinity within the structure,compared to those reported for Li₁₀SnP₂S₁₂ and Li₁₀GeP₂S₁₂. Furthermore,negligible features of Li₂S (e.g., standard peak positions for Li₂S)appear in each of the spectra, indicating that a chemical reactionoccurred (and not, for example, a mere mechanical mixture of thestarting compounds).

Example 2

This example demonstrates the stability of the ionically conductivecompound Li₂₀SiP₂S₁₇ in the presence of an electrolyte.

FIG. 5 shows XRD patterns from particles of Li₂₀SiP₂S₁₇ before and aftersoaking in an LP30 electrolyte (1M of LiPF₆ in a 1:1 ratio of ethylcarbonate and dimethyl carbonate) for 3 weeks at 40° C. The XRD patternsdemonstrate very similar structure before and after the electrolytesoak.

Example 3

This example demonstrates the stability of lithium in the presence ofthe ionically conductive compounds described herein.

Stability in the present of lithium was tested using sandwich structuresin which a pellet of particles of an ionically-conductive compound(e.g., Li₁₀SiP₂S₁₂, Li₂₀SiP₂S₁₇ or Li₂₄SiP₂S₁₉, e.g., between 0.5 to 2mm in average thickness) was placed between two lithium metal foils.

In a sandwich structure, Li/Li₁₀SiP₂S₁₂/Li, the lithium metal wasconsumed over time, which indicated that the material was not stableagainst lithium metal. Structures incorporating Li₂₀SiP₂S₁₇ orLi₂₄SiP₂S₁₉, such as Li/Li₂₀SiP₂S₁₇/Li and Li/Li₂₄SiP₂S₁₉/Lirespectively, demonstrated an improved stability next to lithium metalcompared to Li₁₀SiP₂S₁₂. Stability was also confirmed qualitatively byopening the structures (e.g., Li/Li₁₀SiP₂S₁₂/Li) and observing changesin the pellet layer.

Example 4

This example describes the conductivity and structure of an ionicallyconductive compound having the formula Li₂₁S₁₇GaP₂ (i.e., Formula (I):Li_(2x)S_(x+w+5z)M_(y)P_(2z), where x is 10.5, y is 1, w is 1.5y, z is1, and M is Ga).

An ionically conductive compound was formed by mixing Li₂S, GaS₂, andP₂S₅. The mixture was mixed by ball milling. The mixture was sealed in aclosed vessel under inert atmosphere (e.g., Argon) and heated to 700° C.for between 12-16 hours. The vessel was then cooled to room temperatureand the material was ground into powder form to form Li₂₁S₁₇GaP₂.

The average ionic conductivity of Li₂₁S₁₇GaP₂ was 1.4×10⁻⁴ S/cm. Theaverage ionic conductivity was measured by pressing the particlesbetween two copper cylinders at a pressure of up to 4 tons/cm², anddetermining the conductivity using a conductivity bridge operating at 1kHz at 25° C., at 500 kg/cm² increments of pressure until changes inaverage ion conductivity were no longer observed in the sample.

Example 5

This example demonstrates the stability of the ionically conductivecompound Li₂₂SiP₂S₁₈ in the presence of an electrolyte.

FIG. 6 shows XRD patterns from particles of Li₂₂SiP₂S₁₈ before and aftersoaking in an organic liquid carbonate-based electrolyte for 2 weeks at40° C. The XRD patterns demonstrate very similar structures before andafter the electrolyte soak, showing that the compound is stable in thiselectrolyte.

Comparative Example 5

This example demonstrates the stability of the ionically conductivecompound Li₁₈P₃S₁₅Br₃ in the presence of an electrolyte.

FIG. 7 shows XRD patterns from particles of Li₁₈P₃S₁₅Br₃ before andafter soaking in an organic liquid carbonate-based electrolyte for 2weeks at 40° C. A white thick powder formed around the particles. TheXRD patterns and white powder suggest that the Li₁₈P₃S₁₅Br₃ particlesreacted with the electrolyte.

Example 6

This example describes the conductivity and composition of variousionically conductive compounds having the formulaLi_(2x)S_(x+w+5z)M_(y)P_(2z), where x is 5.5-10.5, y and z are 0.5-2, wis y, 1.5y, or 2y, and M is Si, Al, La, B, and/or Ga.

A comparative compound having the formula Li₂₁AlSi₂S₁₆ (substituting Alfor P), was also created.

Ionically conductive compounds were formed by mixing of Li₂S, SiS₂,P₂S₅, and/or using different precursors like Li₂S, Si (or Al, La, B,and/or Ga), S₈, P₂S₅, or Li₂S, Si, S₈, P according to stoichiometry toform the compounds as listed in Table 2. The mixtures were mixed by ballmilling. The mixtures were sealed in a closed vessel under an inertatmosphere (e.g., argon) and heated to 500° C. or 700° C., as noted, forbetween 12-16 hours. The vessels were then cooled to room temperatureand the materials were ground into powder form.

The conductivity of particles of ionically conductive compounds havingthe formula L_(2x)S_(x+w+5z)M_(y)P_(2z), is summarized in Table 2. Theaverage ionic conductivity was measured by pressing the particlesbetween two copper cylinders at a pressure of up to 4 tons/cm², anddetermining the conductivity using a conductivity bridge operating at 1kHz at 25° C., at 500 kg/cm² increments of pressure until changes inaverage ion conductivity were no longer observed in the sample.

TABLE 2 Conductivity Synthesis Temperature (° C.) [mS/cm]Li₂₁SiP₂S_(17.5) 700 2.5 Li₂₁La_(0.5)Si_(1.5)PS_(16.75) 700 2.1Li₂₁LaSiPS_(16.5) 700 1.0 Li₂₁La₂PS₁₆ 700 0.0011 Li₂₁AlP₂S₁₇ 700 0.0029Li₁₇AlP₂S₁₅ 700 0.0039 Li₁₇Al₂PS₁₄ 700 0.0031 Li₁₁AlP₂S₁₂ 700 0.0026Li₁₁AlP₂S₁₂ 500 0.13 Li₂₁AlSiPS_(16.5) 700 0.57Li₂₁Al_(0.5)Si_(1.5)PS_(16.75) 700 0.71 Li₂₁AlSi₂S₁₆ 700 0.03 Li₂₁BP₂S₁₇700 0.094 Li₂₁GaP₂S₁₇ 700 0.14

While several embodiments of the present invention have been describedand illustrated herein, those of ordinary skill in the art will readilyenvision a variety of other means and/or structures for performing thefunctions and/or obtaining the results and/or one or more of theadvantages described herein, and each of such variations and/ormodifications is deemed to be within the scope of the present invention.More generally, those skilled in the art will readily appreciate thatall parameters, dimensions, materials, and configurations describedherein are meant to be exemplary and that the actual parameters,dimensions, materials, and/or configurations will depend upon thespecific application or applications for which the teachings of thepresent invention is/are used. Those skilled in the art will recognize,or be able to ascertain using no more than routine experimentation, manyequivalents to the specific embodiments of the invention describedherein. It is, therefore, to be understood that the foregoingembodiments are presented by way of example only and that, within thescope of the appended claims and equivalents thereto, the invention maybe practiced otherwise than as specifically described and claimed. Thepresent invention is directed to each individual feature, system,article, material, kit, and/or method described herein. In addition, anycombination of two or more such features, systems, articles, materials,kits, and/or methods, if such features, systems, articles, materials,kits, and/or methods are not mutually inconsistent, is included withinthe scope of the present invention.

All definitions, as defined and used herein, should be understood tocontrol over dictionary definitions, definitions in documentsincorporated by reference, and/or ordinary meanings of the definedterms.

The indefinite articles “a” and “an,” as used herein in thespecification and in the claims, unless clearly indicated to thecontrary, should be understood to mean “at least one.”

The phrase “and/or,” as used herein in the specification and in theclaims, should be understood to mean “either or both” of the elements soconjoined, i.e., elements that are conjunctively present in some casesand disjunctively present in other cases. Multiple elements listed with“and/or” should be construed in the same fashion, i.e., “one or more” ofthe elements so conjoined. Other elements may optionally be presentother than the elements specifically identified by the “and/or” clause,whether related or unrelated to those elements specifically identified.Thus, as a non-limiting example, a reference to “A and/or B”, when usedin conjunction with open-ended language such as “comprising” can refer,in one embodiment, to A only (optionally including elements other thanB); in another embodiment, to B only (optionally including elementsother than A); in yet another embodiment, to both A and B (optionallyincluding other elements); etc.

As used herein in the specification and in the claims, “or” should beunderstood to have the same meaning as “and/or” as defined above. Forexample, when separating items in a list, “or” or “and/or” shall beinterpreted as being inclusive, i.e., the inclusion of at least one, butalso including more than one, of a number or list of elements, and,optionally, additional unlisted items. Only terms clearly indicated tothe contrary, such as “only one of” or “exactly one of,” or, when usedin the claims, “consisting of,” will refer to the inclusion of exactlyone element of a number or list of elements. In general, the term “or”as used herein shall only be interpreted as indicating exclusivealternatives (i.e. “one or the other but not both”) when preceded byterms of exclusivity, such as “either,” “one of,” “only one of,” or“exactly one of.” “Consisting essentially of,” when used in the claims,shall have its ordinary meaning as used in the field of patent law.

As used herein in the specification and in the claims, the phrase “atleast one,” in reference to a list of one or more elements, should beunderstood to mean at least one element selected from any one or more ofthe elements in the list of elements, but not necessarily including atleast one of each and every element specifically listed within the listof elements and not excluding any combinations of elements in the listof elements. This definition also allows that elements may optionally bepresent other than the elements specifically identified within the listof elements to which the phrase “at least one” refers, whether relatedor unrelated to those elements specifically identified. Thus, as anon-limiting example, “at least one of A and B” (or, equivalently, “atleast one of A or B,” or, equivalently “at least one of A and/or B”) canrefer, in one embodiment, to at least one, optionally including morethan one, A, with no B present (and optionally including elements otherthan B); in another embodiment, to at least one, optionally includingmore than one, B, with no A present (and optionally including elementsother than A); in yet another embodiment, to at least one, optionallyincluding more than one, A, and at least one, optionally including morethan one, B (and optionally including other elements); etc.

It should also be understood that, unless clearly indicated to thecontrary, in any methods claimed herein that include more than one stepor act, the order of the steps or acts of the method is not necessarilylimited to the order in which the steps or acts of the method arerecited.

In the claims, as well as in the specification above, all transitionalphrases such as “comprising,” “including,” “carrying,” “having,”“containing,” “involving,” “holding,” “composed of,” and the like are tobe understood to be open-ended, i.e., to mean including but not limitedto. Only the transitional phrases “consisting of” and “consistingessentially of” shall be closed or semi-closed transitional phrases,respectively, as set forth in the United States Patent Office Manual ofPatent Examining Procedures, Section 2111.03.

What is claimed is:
 1. An article for use in an electrochemical cell,comprising: a compound of formula (I):Li_(2x)S_(x+w+5z)M_(y)P_(2z)  (I) wherein: M is selected from the groupconsisting of Lanthanides, Group 3, Group 4, Group 5, Group 6, Group 7,Group 8, Group 9, Group 12, Group 13, and Group 14 atoms, andcombinations thereof; x is 8-16, y is 0.1-6, w is 0.1-15, and z is0.1-3.